key: cord-007654-lchdm4xr
authors: Liu, Yang; King, Nicholas; Kesson, Alison; Blanden, Robert V.; Müllbacher, Arno
title: Flavivirus infection up-regulates the expression of class I and class II major histocompatibility antigens on and enhances T cell recognition of astrocytes in vitro
date: 2002-12-11
journal: J Neuroimmunol
DOI: 10.1016/0165-5728(89)90171-9
sha: 
doc_id: 7654
cord_uid: lchdm4xr

West Nile virus (WNV) infection of astrocytes can up-regulate their expression of both class I and class II major histocompatibility complex (MHC) antigens as determined by flow cytometry with monoclonal antibodies specific for class I and class II MHC antigens. The up-regulation of class I MHC antigen expression could be partly caused by interferon secreted after WNV infection because the synthetic interferon inducer polyinosinic-polycytidylic acid (poly I : C) has similar effects. In contrast the up-regulation of class II MHC antigen expression was not induced by poly I : C. The increased MHC antigen expression by WNV infection had significant effects on T cell recognition. Thus, WNV and influenza virus A/WSN double-infected astrocytes but not astrocytes infected by A/WSN alone were lysed by influenza virus-immune cytotoxic T cells. Similarly, WNV-infected astrocytes were better stimulators than normal astrocytes for a class II MHC-reactive T cell line, both in terms of T cell proliferation and interleukin release.

It is well established that the major histocompatibility complex (MHC) antigens form an essential part of antigenic structures recognised by T iymphocytes (reviewed by Zinkernagel and in the case of experimental allergic encephalitis of rats, where transfer of syngeneic T cells specific for myelin basic protein (MBP) results in full expression of the disease (Lipton et al., 1976; Tourtellotte et al., 1978; Kreth et al., 1982; Booss et al., 1983; Wekerle et al., 1985) . The paradox has been partly resolved by findings which indicate that at least some cells from the CNS, such as astrocytes, ofigodendrocytes, brain endothelial cells and neurons can be induced to express class I and/or class II MHC antigens by lymphokines such as "t-interferon (T-IFN) and by certain viral infections such as murine hepatitis virus and Theiler's murine encephalomyelitis virus (Hirsch et al., 1983; Massa et al., 1986; Suzumura et al., 1986; Rodriguez et al., 1987) .

Additional data suggested that such elevation of the MHC antigens on astrocytes and/or brain endothelial cells can potentiate the antigen-presenting capacity of these cells Male et al., 1987) . Thus, the induction of expression of MHC antigens on the cells of the CNS could be an important regulatory mechanism in the initiation, amplification and targeting of the local immune response.

The etiology of a number of neurological disease, most notably, multiple sclerosis, still remains a matter of debate. The preferred hypotheses involve an autoimmune phenomenon in which cellular and/or humoral immune responses are directed against constituents of myelin. However, epidemiological data implicate some kind of acquired factor, most likely an infection, in the etiology of multiple sclerosis (Waksman et al., 1986) .

In recent years, evidence has accumulated that viral infections can result in the breakdown of immunological tolerance. Thus both autoreactive B cells (Haspel et al., 1983a, b) and autoreactive T cells (Pfizenmaier et al., 1975; Komatsu et al., 1978) have been observed during viral infection. In this context it would be of interest to study the possible effect of neurotropic viral infection on the local immune response in the CNS.

Flaviviruses are one group of viruses which are responsible for a number of neurological diseases (Monath, 1986) . In this study, we address the effect of West Nile virus (WNV) infection on astrocytes in vitro.

West Nile virus Sarafend strain (WNV) was obtained from Dr. I.D. Marshall and grown either in Vero cells (WNV-V) or in new-born mouse brain (WNV-B). The stocks were prepared and titrated as described (Reed and Muench, 1938; Taylor and Marshall, 1975) . Influenza virus A/WSN was prepared by a standard method (Yap and Ada, 1977) .

Mice were bred under pathogen-free conditions at the Animal Breeding Establishment of the John Curtin School of Medical Research. The strains used were: CBA/H (H-2k), BALB/c (H-2d), B10.T(6R) (KqIqDd), B10.AQR (KqlkDd). Newborn mice were used at 1 or 2 days of age and adult female mice at 6-8 weeks.

Astrocytes were prepared in essentially the same way as has been described (McCarthy and de Vellis, 1980) . Briefly, 1-to 2-day-old CBA/H mice were anesthetized at -20°C for 15 min. After careful removal of the meninges, the brains were broken down by pipetting and were then subjected to treatment with trypsin/DNase I solution (0.1~ trypsin and 0.001~ DNase I, w/v) for 20 min, shaken occasionally. The action of trypsin was stopped by adding equal volumes of neural medium (Dulbecco's minimum essential medium (DMEM) supplemented with L-arginine 12 mg/l, L-asparagine 36 mg/l, folic acid 6 mg/l, v-glucose 7 g/l, and non-essential amino acids 1~ v/v (Flow Laboratories, . The suspe-sion was centrifuged and the pellet was dispersed. These cells were cultures in 80 cm 2 Nunclon plastic flasks at a density of 106/ml. At day 8, the cells were confluent and the medium was changed. One day later, the flasks were shaken for 15-18 h (37°C, 250 rpm). The medium was then sucked off and the cultures were washed with Puck's saline, trypsinized into single-cell suspensions and cultured again. The secondary cultures were tested by indirect immunofluorescence microscopy with rabbit anti-human glial fibrillary acidic protein (GFAP) serum (Dako, Code A561) and shown to he more than 95% GFAP positive. The secondary cultures were used in this study.

After astrocytes were grown to confluency (approximately l0 s cell/well in Linbro 24-well plastic iissue culture plates), the medium was sucked off and West Nile viruses (100 plaque-forming units (pfu)/cell of WNV-B and 20 pfu/cell WNV-V, respectively) were added in 100/LI and incubated at 37 o C for I h. At different times after inoculation, cells were harvested and frozen at -20 ° C. Free virus was obtained by freeze-thawing plus ultrasonication as described (Taylor and Marshall, 1975) .

The protocol is essentially the same as described by De Clercz (1981) . Briefly, astrocytes were grown in 24-well tissue culture trays until confluency; the cultures were then exposed to poly I:C (Sigma, 25/Lg/ml) for 8 h and washed with DMEM medium 3 times. Fresh neural medium was added and the cultures were further incubated for 40 h. The supernatants were harvested and IFN activity determined.

IFN was assayed by inhibition of viral RNA synthesis in L929 cells as described by Morris et al. (1987) . The titer of IFN was defined as reciprocal of the final dilution that gave 50% inhibition of Semliki Forest virus RNA synthesis.

100/11 of 1 : 20 dilution of supernatants from 48 h WNV-B-infected astrocytes were incubated with an equal volume of medium or 100 units of rabbit antiserum to mouse IFN (a +/]) (Lee Biomedical Research, Cat. No. 21031) at 37°C for 1 h. The IFN activity of these supernatants was titered as described above.

Spleen cells from B10~T(6R) mice (KqlqD d) were stimulated with those from B10.AQR (KqlkD d) as described (King et al., 1986) for 159 three passages. At the fourth passage, an enriched medium for T cell lines (DMEM supplemented with 2 x 10 -4 M 2-mercaptoethanol, 10~ fetal calf serum (FCS) and 5% concanavalin A (ConA)-activated spleen cell supernatant (CS) prepared as described by Sinickas et aL (1985a) ) was added together with allogeneic stimulators.

Generation of secondary cytotoxic T cells against influenza virus A/WSN and primary allo-reactive cytotoxic T cells has been described in detail (Yap and Ada, 1977; King et al., 1986) .

The method for the L929 target system has been described (Yap and Ada, 1977) . WNV-V-infected or uninfected astrocytes were cultured in flat-bottomed tissue culture plates at 37°C for 48 h. These cultures were then reinfected with influenza virus A/WSN (3 EID~o/Cell) and labeled with 51Cr by adding 25 /~1 medium containing 6 x 104 EIDs0/well influenza virus A/WSN and 1:10 dilution of Na2SlCr204 and incuba~,A at 37°C for 1 h. The rest of the assay was carried out in the same way as that for L929 targets.

The proliferation of the H-2Ik-reactive T cell line was determined by [3H]methyl-thymidine (Amersham) incorporation as has been described (Sinickas et al., 1985b) . Both spleen cells and astrocytes were used as stimulators. After growth to confluency in 96-well tissue culture plates (approximately 2 × 104 cells/well), the astrocytes were irradiated with 6000 R from a e°Co v-ray source. 10/~g/ml of indomethacin was added to the enriched medium of T cell lines and 150/tl of this medium per well was added together with 2 x 104 cells of an H-21k-reactive T cell line. 24 h later, 0.5 ;tCi/well of the [3H]methyl-thymidine was added. After another 24 h, the cultures were harvested onto glass fiber filter strips and the incorporation of label into DNA was determined by scintillation counting.

WNV-infected or mock-infected astrocytes grown to confluency in 96-well plates (2 x 104/ well) were irradiated with 2000 R and were used as stimulators of 2 × 104 T cells in 0.2 ml DMEM medium per well supplemented with 10 -4 M 2mercaptoethanol, 10 #g/ml indomethacin and 10% FCS. 24 h later the supernatants were collected and their interleukin activity was tested, as described by Lafferty et al. (1980) . It is now known that this assay can measure interleukin-2 (IL-2) and/or imerleukin-4 (IL-4) activity (Severinson et al., 1987) .

Moneclonal antibodies (McAbs) specific for D k, I-A k and I-A a antigens were obtained from the supernatants of cultures of hybridoma clones 15-5-5S, 11-5.2.1.9, and MK-D6 (Oi et al., 1978; Ozato et al., 1980; Kappler et al., 1981) (ATCC Nos. HB-24, T1B-94 and HB-3), respectively, obtained from the American Type Culture Collection. The supernatants were concentrated 10-fold on an American P10 membrane. In adoition, an McAb specific for K k (clone 11-4.1) was purchased from Becton-Dickinson. Rabbit anti-mouse immunoglobulin (RAMIg) was raised in a New Zealand white rabbit, separated from whole serum using a protein A-Sepharose column (Pharmacia) and conjugated to fluorescein-isothiocyanate (FITC) by standard methods ((3oding, 1976) .

Astrocvtes ~ ere infected with WNV or treated with recombinant ~-IFN (500 U/ml) or poly I : C for 48 h. S:,ngle-cell suspensions of astrocytes were obtained from the culture vessel by gentle trypsinization. The cells were counted and viability, as measured by trypan blue dye exclusion, was invariably > 95~. All subsequent steps of the labeling procedure were carried out at 4 ° C. Samples of 3 × l0 s astrocytes were incubated in 100 /L1 of anti-MHC antibody for 60 rain. After the first antibody incubation the cells were centrifuged through a bed of 500 pl FCS, the supernatant removed, and the astrocytes resuspended in 100/~1 of RAMIg-FITC for a further 60 min at a dilution giving saturation labeling (determined by prior titration). Following this incubation, the cells were centrifuged through an FCS bed and resuspended in 250 #1 DMEM for flow cytometry.

Fluorescence was measured using a FACS IV (Beckton-Dicldnson) equipped with an argon ion laser set at the standard excitation wavelength of 488 nm for FITC. Emitted fluorescence between 515 and 540 nm was measured. 3 × 104 cells were analyzed from each labeled sample.

In no experiment did any of the astrocyte sample populations show changes detectable by lowangle (cell size) or right-angle (membrane configuration) scatter analysis on the FACS. Thus we presume that differences in the MHC fluorescence distributions between astrocyte groups reflect a ~:hange in the cell surface MHC antigen concentration.

Astrocytes grown to confluency in 24-well tissue culture plates were infected with either 100 pfu/cell of WNV-B or 20 pfu/cell of WNV-V, and viral titers at different times after infection were determined. Titers dropped about 100-fold within 12 h (Table 1) . However, a clear increase in viral titers was observed by 36 h. The titers reached a plateau at 48 h after infection and remained at a similar level for at least 1 week. Further experiments revealed that viral antigens became detectable after 24 h by immunofluorescence microscopy and by 40 h 50-60~ of the astrocytes were expressing detectable viral antigen. The proportion of viral antigen-positive cells remained at a similar level for at least 2 weeks. These data show that WNV can productively infect some cells in astrocyte populations.

Astrocyte cultures, either infected with WNV or treated with poly I:C, were tested for their ability to produce IFN. High titers of IFN were detected in the supernatant of astrocytes infected by WNV-B or WNV-V, or treated by poly I : C, all for 48 h ( Table 2 ). The IFN titers were 4-fold 7.0 6.5 60 6.7 6.5 72 6.7 6.3 84 6.7 6.5 96 6.5 6.0 144 6.5 6.5

• West Nile virus prepared from mouse brain. b West Nile virus prepared from Verb cell line.

lower in the supernatant of poly l:C-treated astrocytes than that of WNV-infected astrocytes. Furthermore, the IFN produced in WNV-B-Infected astrocytes can be neutralized by antibody specific for IFN (a + ~8), hence the IFN produced is a-and/or p.IFN (Fig. 1) .

The expression of class I MHC antigens on CBA/H astrocytes was investigated by flow cytometry. The single-cell suspensions were stained with McAbs specific either for H-2D k or H-2K k. After the astrocytes were infected by WNV-V for 48 h, the expression of H-2K ~ as determined by peak fluorescence increased by more than 2-fold compared to mock-infected astrocytes (Fig. 2a) . The binding of the McAb to the H-2K k was specific as an isotype control McAb specific for H-21-A d (HB-3) did not bind significantly to either normal or WNV-infected astrocytes. Similar enhancement was observed in H-2D k expression (Fig.  2b) . As both WNV-B and WNV-V are potent IFN inducers (Table 2) , the question arose as to whether the elevation in MHC antigen expression was due *.o the IFN produced. To investigate this question a synthetic IFN inducer, poly I:C was used. As shown in Fig. 2c , poly I : C treatment can significantly enhance the expression of class I MHC antigens, which admits the possibility that the enhanced expression after WNV infection is at least partly the result of virus-induced IFN.

As class I MHC antigens are the major restric- In each case astrocytes were treated for 48 h.

virus-immune Tc (Table 3 ). In contrast, astrocytes infected by influenza virus or WNV alone were not lysed by influenza virus-immune Tc more than normal astrocytes. The activity of the Tc was confirmed as *.hey lysed influenza virus-infected L929 (H-2 t) cells, but not mock-infected L929 cells. This result revealed that WNV infection enhances MHC-restricted virus-specific Tc recognition on astrocytes. Lysis of WNV-infected astrocytes by BALB/c anti-CBA/H alloreactive T cells was significantly higher than that of normal astrocytes while comparable to the lysis of y-IFN-treated astrocytes (Fig. 3) , hence WNV infection enhances ulloreactive Tc recognition on astrocytes. 

The expression of cell surface cl~s II MHC antigens on CBA/H astrocytes was also determined by flow cytometry. Astrocytes were labeled with H-2I-Ak-specifi¢ McAb TIB94; control cells were treated with HB-3, an McAb specific for H-21-A d. Normal CBA/H (H-2 k) astrocytes 163 express little or no detectable class II MHC antigens, as their binding to TIB94 (H-21-Ak-speeific) is not significantly higher than to HB-3 (H-2I-A dspecific) (Fig. 4a) . However, after the astrocytes were infected by WNV-B for 48 h, a distinct increase in expression of H-21-A k antigen was detected Fig. 4b) , although the amount of H-2I-A k expressed on WNV-infected astrocytes was not as , and astrocytes treated with "g-IFN (C). c: As for b, but normal astrocytes (A) and astrocytes treated with poly 1 : C (B). d: As above but astroq,'tes infected by WNV-V. Ast.~ocytes were subject to pre-treatment with WNV or IFN or poly I : C for 48 h before labeling. much as that on y-IFN-treated astrocytes. The specificity of the labe~ng was ascertained in two ways: (a) HB-3 (anti-H-2I-A °) McAb dad not bind WNV.infected CBA/H (H-2 k) astrocytes (Fig.  2a) ; (b) as HB-3 is of the IgG2a subclass, while TIB~ is IgG2b, another IgG2b McAb specific for murine CD4 was tested and shown not to bind either WNV-infected or normal astrocytes (data not shown). It seems unlikely that material other than WNV in WNV-B (e.g. murine IFN) is responsible for the up-regulation of class II MHC antigen, as WNV-V that was passaged 4 times in Veto cells (a permanent cell line originating from monkey kidney that does not secrete murine IFN) also consistently up-regulated class II MHC antigen, though to a lesser extent than WNV-B in this particular experiment (Fig. 4d) . Furthermore, poly I :C, which "nduced IFN production and enhanced class I MHC antigen expression in astrocyte cultures (Fig. 2c , Table 2 ) dad not induce class II MHC ant/gen expression (Fig. 4c) . The mechanism of the induction of class II MHC antigen is at present unknown.

An alloreactive B10.T(6R) anti-B10.AQR T cell line specific for H-2I k antigens was used to de-TABLE 4 termine if the WNV-induced expression of class II MHC antigens on astrocytes can be recognised by T cells. The T cell line was induced to proliferate by spleen cells from mice bearing H-2I k antigens, e.g. B10.AQR and CBA/H mice, but not by antologous B10.T(6R) spleen cells (Table 4 , Expt. 1).

WNV-infected CBA/H astrocytes also stimulated the proliferation of the H-2Ik-reactive T cell line (Table 4 , Expt. 2). The stimulation was comparable to CBA/H spleen cells; mock-infected astrocytes had no stimulation effect. To test whether the induced stimulation effect of astrocytes was due to induced ¢lass II MHC antigens on their surface, the H-2I-Ak-specific McAb TIB94 was added. TIB94 blocked the proliferation of the H-21k-specific cell line stimulated by either B10.AQR spleen cells or by WNV-V-infected CBA/H astrocytes ( WNV-infected and uninfected astrocytes were also compared for their ability to stimulate IL-2 and/or IL-4 release from the H-2Ik-specific T cell line described above. WNV-infected CBA/H astrocytes stimulated Significant release of IL-2 and/or 1L-4, whereas uninfected CBA/H astrocytes were, much poorer stimulators (Fig. 5) . The quantity of IL-2 and/or IL-4 released was about 25-fold higher with WNV-infected astrocytes than with normed astrocytes. Specificity of the stimula- WNV-infected CBA/H astrocytes stimulated significantly IL-2 and/or IL-4 release from the primary H-2Ik-reactive T cell population, while co!s the normal astrocytes induced essentially no IL-2 and IL.4 release (Fig. 6 ).

Since it was established that MHC antigens formed an important part of the antigenic struc-165 ture recognised by T lymphocytes (Zinkernagel and Doherty, 1979; Schwartz, 1986) , there "has been great interest in the regulation of MHC antigen expression on potentJal antigen-presenting cells. It is well documented that different virus infections may either inhibit or enhance the expression of MHC antigens, Notably, infection by adenovirus (F~i~lbo et al., 1986) , herpes simplex virus type 2 (Jennings et aL, 1985) , ectromeiia virus (Gardner et al., 1975) and measles virus (Rager-Zisman et al., 1981) can down-regulate class I MHC antigen expression of their host cells and may make the latter less susceptible to cytotoxic T cells. On the other hand, murine hepatitis virus (Massa et al., 1986; Suzumura et al., 1986 ), Epstein-Barr virus (McCune et al., 1975 , Moloney murine leukemia virus (Flyer et ai., 1985) and Theiler's murine encephalomyelitis virus (Rodriguez et al., 1987) can up-regulate class I and/or class II MHC antigen expression. Our results described here revealed that flavivirus infection can up-regulate the e:~pression of cell surface class I and class 1I I~,~HC antigens. It has been docuraented that interferon can up-regulate class ! and II MHC antigen. All three classes of IFN L~own (a, t, ~,) have been reported to enhance ,class I MHC antigen expression, while only ~,-IFN can up-regulate the expression of class II MHC ~mtigens OVong et al., 1985) . In our experiment, any treat~ent that can induce IFN production, e.,g. WI,4V-B and WNV-V infection or poly I : C treatmen~,, can up-regulate class I MHC antigens; it is possible ~hat the up-regulation of class I MHC antigen expression by WNV infection is at least patti3, the result of IFN produced after virus infection. In contrast, poly I:C treatment of astrocytes, which induces good IFN production and increases class I MHC antigen expression equal to or more than WNV infection, fails to induce class II MHC antigen expression. This finding together with the data that IFN produced in WNV-B-infected astrocyte culture can be neutralized by anti-(a + fl)-IFN antibody strongly suggests that the induction of class II MHC antigen by WNV does not depend on IFN produced. Addition of antibodies that neutralize y-IFN to WNV-infected astrocytes culture would help to answer the question if free v-IFN was involved in class II MHC antigen induction. However, the question as to what extent virus replication per se and induced interferon actually contribute to enhanced class I MHC expression is more problematic. Some obviol:s approaches used by others (Massa et al., 1986) , i.e. use of ultraviolet-inactivated virus and neutralizing McAb to the virus cannot provide definile information, because it is not known to what extent UV inactivation will inhibit viral protein and nucleic acid synthesis and the mechanism of viral neutralization is at present not well understood. Furtherraore, addition of IFN antibody may not help to exclude the role of IFN due to the autocrine activity without the need of secretion (Sanceau et al., 1987) .

It seems unlikely that the binding of H-2I-A k-speo_P._c McAb to WNV-infected but not normal astrocytes of CBA/H(H-2 k) was due to the molecular mimicry by a viral product of an epitope on the I k molecule, because an McAb specific for H-21-A d can bind to WNV-infected astrocytes from BALB/c(H-2 d) mice but cannot bind to WNV-infected astrocytes from CBA/H(H-2 k) mice; WNV can. repUcate productively in astrocytes from both strains of mice (data not shown).

A number of studies have shown that treatment which up-regulates the expression of cell surface class I MHC antigens increases the susceptibility of cells to lysis by appropriately sensitised Tc cells, probably due to recognition by low-affinity clones that could not exhibit cytotoxic activity without the elevation of MHC antigen expression (Shimoukevitz et al, 1985) . Infection by viruses that down-regulate cell surface MHC antigen expression, on the other hand, results in reduced susceptibility of the infected cells to lysis by virus-specific cytotoxic T cells. Thus it has l~een shown that herpes simplex virus type 2 infection, which down-regulates cell surface MHC expression, reduces the susceptibility of an SV40-and HSV2-double-infectezl targets to lysis by SV40specific Tc cells, as compared to target cells infected with SV40 alone (Jennings et al., 1985) . Adenovirus type 5 infection inhibits the cell surface expression of class I MHC antigen via the E3 protein. This phenomenon results in less efficient recognition by adenovirus-specific Tc cells of target cells infected by this wild-type virus compared to target cells infected by an E3 deletion mutant which has no effect on host MHC antigen expression (Miillbacher and Bellett, personal communication) and could be responsible for the tumorigenicity of the wild-type virus (Eager et al., 1985) . A Moloney murine leukemia virus that increases cell surface class I MHC antigen expression was also reported to increase the susceptibility of host cells to lysis by alloreactive Tc cells (Flyer et al., 1985) . However, no attempt was made to address the effect of up-regulated MHC antigen expression on the recognition of MHC-restricted, antigen-specific T ells. In this paper, we compared WNV.infected astrocytes with uninfected controls for their ability to act as targets of influenza virus-specific Tc cells and as stimulators for an Ik-reactive T cell line. The results showed that WNV infection has significant effects on T cell recognition of astrocytes. 'Ilms, after infection by influenza virus, normal astrocytes are poor targets of influenza virus-specific Tc, while doubly infected (with WNV and influenza) astrocytes can be well recognized by influenza-specific Tc. WNV-infected astrocytes from CBA/H mice can also stimulate Ik-reactive T cells significantly better than the normal astrocytes, in terms of both T cell proliferation and interleukin release. The latter function was also enhanced in populations of primary anti-H-2I k T cells. These findings are particularly interesting because astrocytes are a large population of cells in the CNS, presumably important both for the physiology and immunology of the CNS (Fontana e~ al., 1985) . Elevated T cell recognition of astroeytes could have an important effect on the organism. These findings also raise interesting questions regarding self tolerance. If T cell tolerance to self antigens is determined quantitatively (Blanden et al., 1987) the up-regulation of MHC antigens in the CNS could possibly break T cell self tolerance in the CNS. This may explain the autoimmune/virai etiology of some neurological diseases.

Quantitative considerations of T cell activation and self-tolerance

Immunohistological analysis of T lymphocyte subsets in the central nervous system in chronic progressive multiple sclerosis

Interferon induction by polynucleotides, modified polynucleotides, and polycarboxylates

Expression of histocompatibility antigens H-K. -D, and -L is reduced in adenovirus-12-transformed mouse cells and is restored by interferon

~1985) Astrocytes as antigen-presenting cells. I. Induction of la antigen expression on astrocytes T cells via in-anune interferon and its effect on antigen presentation

Retrovirus induced changes in major histocompatibility complex antigen expression influence susceptibility to lysis by cytotoxic T lymphocytes

The endothelium-astrocyte immune control system

Cell mediated cytotoxicity against ectromelia virus-infected target cells

Conjugation of antibodies with fluorochromes: modrficat!ous to the standard methods

Viral induced autoimmnnity: monoclonai antibb.lies that react with endocrine tissues

Multiple organ-re.~ctive monoclonal autoantibodies

Expression of la antigens by cultured estrocytes treated with y-interferon

Quantitative variation in la antigen expression plays a central role in immune regulation

Effect of herpes simplex virus type 1 and 2 on surface expression of class ! major histecompatibility complex antigens on infected cells

Antigen-inducible, H-2-restricted interleukin-2-producing T cell hybridomas lack of independent antigen and H-2 re. cognition

Relationship between surface H-2 concentration, size of different target cells and lysis by cytotoxic T cells

Clones of cytotoxic lymphocytes can recognize uninfected cells in a primary response against influenza virus

Immunohistochemical identification of T lyn~lphocytes in the central nervous system of patients with multiple selerosis and subacute sclerusilag panencephalitis

An improved assay for interleukin-2 (lymphocyte growth factor) produced by mitogen activated lymphocytes

Theiler's virus-induced demyelination: prevention by immunosuppression

Preparation of separate astre~lJial and ollgodendroglial cell cultures from rat cerebral tissue

Enhanced representation of HL-A antigens on human lymphocytes after mitogenesis induced by phytohemagglutinin of Epstein-Barr virus

Antigen presentation in brain: MHC induction on brain end~ thdium and astrocytes compared

Viral particles induce la antigen expression on astrocytes

Pathobiology of flaviviruses

Infection of cultured mnrine brain cells by Semliki Forest virus: effect of interferon-o.~ on viral replication, viral antigen display, major histocompafibility complex antigen display and lysis by cytotoxie T lymphocytes

Properties of mo~clonal antibodies to mouse Ig allotypes, H-2 and Ia antigens

Hybridoma cell lines secreting monoclonal antibodies to mouse H-2 and la antigens

Adenoviruses of subgenera B, C, D, and E modulate cell-surface expression of major histccompatibility complex class I antigens

Temporary pr~-~,ence of self-reactive cytotoxic T iymphocytes during murine lymphocytic choriomeningitis

Decreased expression of H-2 antigens following acute measles virus infection

A simple method of estimating fifty percent end points

hlunone response geue products (la antigens) on gliai and endothelial cells in virus induced demyelination

Intracellular v-interferon triggers an antiviral state in transformed L cells

Immune response (It) gene of the murine major histocompatibility complex

Interlenkin 4 (IgGI induction factor): a multifunctional lymphokin acting also on T cells

Clonal analysis of cytolytic T lymphocyte-mediated lysis of target cells with inducible antigen expression: correlation between antigen density and requirement for Ly-2/3 function

l~e cytotoxic response to murine cytomegalovirus. I. Parameters in vivo

The cytotoxic response to murine cytomegalovirus. II. In vitro requirement for generation of cytotoxlc T cells

Coronavirus infection induces H.2 antigen expression on oligodendrocytes and astrocytes

Adaption studies with Ross River virus: laboratory mice and cell cultures

Multiple sclerosis: the blood-braln barrier and the measurement of de novo central nervous system of Ig synthesis

Viral etiology of multiple sclerosis: where does the truth fie'?

T lyraphocyte auto-inununity in experimental autoimmune encephalomyelitis

Dist~bution and quantitation of HLA-ABC and DR (Ia) antigens on human kidney and other tissues

Inducible expression of H-2 and la antigens on brain cells

Interferon-v induces the expression of H-2 and la antigen on brain cells

Cytotoxic T cells specific for influenza virus infected target cells

MHC-restricted cytotoxic T cells: studies on the role of polymorphic major transplantation antigens determining T cell restrictionspecificity, function and responsiveness

We thank Boehringer Ingelheim for the kind gift of recombinant 7-IFN and Barb Geary for typing the manuscript. Part of the work was carried out when one of us (Y.L.) was a recipient of a World Health Organisation Fellowship.