121J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 Original Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients Hazhar M. Balaky1*, Akam Jasim Mustafa2, Parween Abdulsamad Ismail3, Araz Muhammad Yousif4 1Mergasor Technical Institute, Erbil Polytechnic University, Erbil, Iraq. 2Department of Chemistry, Faculty of Science, Soran University, Soran, Kurdistan Region, Iraq. 3Department of Chemistry, College of Education, University of Salahaddin, Erbil, Iraq. 4Basic Science Department, Dentistry College, Hawler Medical University, Erbil, Iraq. *Correspondence to: Hazhar M. Balaky (E-mail: hazharbalaky86@yahoo.com) (Submitted: 04 January 2023 – Revised version received: 27 January 2023 – Accepted: 15 February 2023 – Published online: 26 April 2023) Abstract Objectives: This study set out to determine how Calprotectin and B cell activating factor contributes to early COVID-19 patient severity prediction. Methods: The study included 25 healthy controls and 52 patients with SARS-COV2 infection who were clinically diagnosed with COVID-19 illness and were between the ages of 23 and 35. The serum levels of CALP and BAFF were measured using the ELISA method. To gauge CRP levels, an immunoturbidometric assay was performed. Results: Variations in serum levels of CALP and BAFF were found to be statistically insignificant in the study (P = 0.7109 & P = 0.7575, respectively). When compared to the control group (103.95 ± 36.67 ng/mL; 403.03 ± 1.03), COVID-19 patients had non-significantly raised levels of CALP and BAFF (106.5 ± 4.67 ng/mL; 436.9 ± 12.77 pg/mL, respectively). According to ROC curve analysis, the area under the receiver operating characteristics curve (AUC) for CALP and BAFF was (0.5170) and (0.5259), respectively. (r = 0.6923; P = 0.0001). There was a significant positive correlation between serum CALP and BAFF levels. The connection between serum CRP levels and CALP (r = 0.3010; P = 0.1271) and BAFF levels (r = 0.2912; P = 0.1406) was insignificantly positive. Conclusion: The current study’s findings suggested that serum CALP and BAFF concentrations were increased in COVID-19 patients, suggesting that these inflammatory markers may be helpful indicators of the severity of COVID-19. Keywords: Calprotectin, B cell activating factor, C-reactive protein, COVID-19 ISSN 2413-0516 Introduction A pneumonia outbreak was reported in Wuhan (Hubei Prov- ince, China) in December 2019 due to infection with a new coronavirus strain that causes the severe acute respiratory syndrome known as severe acute respiratory syndrome coro- navirus 2 (SARS-CoV-2). The coronavirus disease 19 (COVID-19) pandemic caused by this virus has affected mil- lions of individuals worldwide.1 COVID-19 is associated with several clinical signs and symptoms frequently seen in auto- immune illnesses, including arthralgias, myalgias, exhaus- tion, sicca, and rashes.2 Patients with COVID-19 have also been noted to exhibit thrombosis, myositis, myocarditis, arthritis, encephalopathy, and vasculitis, in addition to these less typical autoimmune disease symptoms.3 These clinical data, along with the rising number of “recovered” patients referred to as “long haulers” or “long COVID” who still exhibit post-COVID-19 symptoms, raise the hypothesis that inflammation in response to SARS-CoV-2 infection increases tissue damage during the acute phase and has some long- term consequences.4 Furthermore, severe COVID-19 is more likely to occur in persons with underlying conditions such as diabetes, hyper- tension, cardiovascular disease, and lung disease, and the age-related case fatality rate increases significantly.5 Since the virus’s introduction, it has been of utmost importance to com- prehend immunity to the virus, the kinetics and protective function of the immune response in the community, and the level of exposure as measured by serosurveys.6 Neutrophil activation signature Calprotectin has become a useful biomarker during the first wave of the pandemic to assess COVID-19 patient risk.7 The self-aggravating thrombo-inflammatory storm in people with severe COVID-19 may be directly attributed to the neutrophil-re- lated inflammatory marker termed Calprotectin. Silvin et al.8 revealed the relationship between elevated Calprotectin levels and immature neutrophils and nonclassical monocytes. He also claimed that increased damage-related molecular pattern creation causes this relationship. In light of this, it has been postulated that Calprotectin is a crucial mediator of the hyper- inflammatory host response and the rise in inflammatory monocytes, neutrophils, and platelets that contribute to the particular coagulopathy in severe COVID-19.1 Additionally, doctors are adopting Calprotectin increasingly frequently to aid in diagnosing and treating a range of different inflamma- tory illnesses due to its stability, assay repeatability, and inex- pensive cost. The molecular functions of CALP in health and unresolved inflammation are poorly understood by most clinicians.9 B-cell activating factor (BAFF), a member of the Tumor Necrosis Factor (TNF) class, is expressed by macrophages, monocytes, dendritic cells, activated neutrophils, and stromal cells.10 First, it has been shown to be necessary for the creation of the humoral response as well as the growth and survival of B lymphocytes.11 Recent research suggests that BAFF may also regulate innate immune responses, particularly at the level of the respiratory mucosa.12 The membrane-bound or soluble protein BAFF, which can induce autoimmune disorders in mice and humans,13 is synthesized excessively. The transmem- brane activator and cyclophilin ligand interactor (TACI), the B cell maturation antigen, and the BAFF receptor are the three known BAFF receptors (BMA). All of these receptors are present in B and T lymphocytes as well as antigen-presenting cells, proving that BAFF action goes beyond B cell biology.14 mailto:hazharbalaky86@yahoo.com 122 J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients Original H.M. Balaky et al. Therefore, this case-control study investigates circulating BAFF and Calprotectin levels, function, diagnostic value, and prognostic relevance in COVID-19 infected patients. Materials and Methods The 77 participants in the present study included 52 con- firmed COVID-19 patients between June 2021 to November 2022 aged (23 to 35 years) and 25 healthy volunteers as the control group. After a COVID-19 clinical diagnosis was made using RT-PCR test, blood samples were taken before the study group’s condition was treated. Each participant’s blood sample was taken at a volume of 5 mL and centrifuged for 15 minutes at 3500 rpm. After that, the serum was frozen and kept at 70°C. The research purpose ELISA kits were used to measure the levels of Calprotectin (CALP) and B-cell activating factor (BAFF) following the manufacturer’s instructions (Sunlong Biotech, China). The CRP levels were measured by immuno- turbidometric assay via a fully automated biochemistry analyzer. Statistical Analysis Statistical analysis was performed using GraphPad prism ver- sion 8 computer program. The Unpaired t-test (Man-Whitney U) was used to compare the biochemical parameters between the study groups. ROC curve analysis and Spearman correla- tion analysis were also performed for biochemical parameters. All comparisons were deemed significant if the P-value was less than 0.05. Results Serum Level of Calprotectin Figure 1 and Table 1 revealed a non-significant elevation (P = 0.7109) in circulating concentration of serum Calprotectin levels in COVID-19 patients (106.5 ± 4.67 ng/mL) as compared to controls (103.9 ± 5.36 ng/mL). Fig. 1 Calprotectin levels between the sera of the studied groups. Table 1. Comparison of CALP and BAFF levels among COVID-19 patients and healthy controls Parameters Controls COVID-19 patients P-value Calprotectin (ng/mL) 103.9 ± 5.36 106.5 ± 4.67 0.7109 B-cell activating factor (pg/mL) 403.0 ± 31.03 436.9 ± 12.77 0.7575 The value expressed in Mean ± SE. Fig. 2 B cell-activating factor (BAFF) levels in sera of the two studied groups. Serum Level of B Cell Activating Factor The results in Figure 2 and Table 1 also showed that there were non-remarkable increase (P = 0.7575) in circulating levels of BAFF in COVID-19 patients (436.9 ± 12.77 pg/mL) as com - pared to healthy controls (403.0 ± 31.03 pg/mL). Relationship Between CALP, BAFF, and CRP in COVID-19 Patients Correlation analysis assessed the relationships among serum CRP levels, CALP and BAFF levels. BAFF and serum CALP levels were positively correlated (r = 0.6923; P = 0.0001) (Figure 3). Figure 3 also shows a non-significant correlation between serum CRP levels and CALP (r = 0.3010; P = 0.1271) and BAFF level (r = 0.2912; P = 0.1406) (Figure 3). These research results may link BAFF activation and the immu- no-inflammatory and pathogenic response, indicating dis- ease activity and tissue damage in various chronic viral infection illness states in COVID-19. ROC Curve Based on the (Receiver Operating Characteristic) ROC curve, the area under the curve (AUC) of serum CALP and Serum BAFF were (0.5170) and (0.5259) respectively (Figure 4). Discussion Serum Level of Calprotectin Numerous recent studies have discovered that patients with coronavirus disease-19 illness had higher Calprotectin levels.1,7 123J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 H.M. Balaky et al. Original Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients Additionally, these investigations have demonstrated that Cal- protectin can predict the need for mechanical breathing, iden- tify death, and differentiate between mild and severe illness states.8,13 Calprotectin is widely distributed in neutrophils, making up around two-thirds of the cytosol’s soluble protein composition. The strong relationship between serum calpro- tectin levels and coronavirus’s present and potential severity indicates that neutrophils are implicated as active promoters of inflammation and respiratory impairment in coronavirus disease. The patients who needed mechanical ventilation while in the hospital also had much greater levels of Calpro- tectin. This data shows a direct link between the Severe acute respiratory syndrome caused by COVID-19, elevated serum calprotectin levels, and neutrophil activation.13 Two studies from medical schools in Michigan, Shanghai, and Washington DC, on the role of Calprotectin as an early indicator of neutro- phil activation in COVID-19 disease. The levels of Calpro- tectin were noticeably elevated in hospitalized individuals with coronavirus illness. Calprotectin levels also correlate with the severity of respiratory failure and the demand for mechan- ical ventilation. This favours using Calprotectin as a biomarker to estimate the severity of a condition and the likelihood that it will result in mortality. Higher levels of Calprotectin were also associated with an increased risk of dying from thrombotic issues.13,15 According to Fig. 3 Correlation of serum CALP with BAFF (a), serum CRP with CALP (b), serum CRP with BAFF (c). Fig. 4 Receiver operating characteristic (ROC) curve analysis of serum CALP levels (a) and BAFF levels (b). recently released research in the academic journal Cell, Calpro- tectin may be able to differentiate between severe and mild COVID-19 disease. The circulating biomarker most obviously elevated in patients with advanced illness was Calprotectin. This study offers future therapeutic strategies explicitly tar- geting Calprotectin to treat the severe form of COVID-19 and shows its potential use in the prognosis of severe disease.8 Sim- ilar to the current study, two inflammation-related biomarkers, Growth Differentiation Factor-15 and Calprotectin, have been researched for their potential role in predicting mortality and disease severity in SARS-CoV-2 infected patients. The study results show that Calprotectin levels are markedly higher in people with COVID-19, and they suggest that Calprotectin may help assess the severity of the illness and forecast in-hospital mortality.1 Calprotectin overexpression may be a direct source of the self-amplifying thrombo-inflammatory storm observed in patients with severe COVID-19. Silvin et al.8 investigation discovered a connection between elevated Calprotectin levels and immature neutrophils and nonclassical monocytes, sup- porting their hypothesis that this correlation originates from the excessive production of damage-associated molecular pat- terns. Due to the host’s hyperinflammatory response and the rise in inflammatory monocytes, neutrophils, and platelets, it has been proposed that Calprotectin is a crucial mediator of specific coagulopathy in severe COVID-19 patients.16 According 124 J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients Original H.M. Balaky et al. and B lymphocytes, are able to produce BAFF.39,40 Interleu- kin-10-producing B cells were enriched and more frequent in chronic hepatitis B patients during hepatic flare-ups, according to a study by Das et al.32 A different study showed that individ- uals with chronic hepatitis B have frequently activated B cells, with an abnormally high proportion of these individuals’ B cells exhibiting activation markers. This demonstrates that this subset of B cells may control T-cell immunity in chronic hepa- titis.31 The intrinsic B-cell activation molecule Fc receptor like1, as well as the B-cell activation markers CD69 and CD86, were also shown to be present in increased amounts in acute and chronic hepatitis B patients.33 These results indicate that B cells are essential for the progression of HBV infection, as well as HBV viral antigens and their interactions with T lymphocytes. Additionally, it was thought that BAFF had a negative impact on the microenvironments of solid and hematological malignancies. So far, it has been demonstrated that BAFF encourages invasive migration in hypoxic breast cancer cell lines.41 Blood BAFF levels, generated by neutrophils, have been linked to oral cavity cancers.42 It has been observed that the prognosis and circulating BAFF levels in multiple mye- loma are related.43 According to Koizumi et al. report.44 It was found that BAFF promoted tumor invasion and dissemination in human pancreatic cancer cases. However, no research has yet been done to determine how BAFF contributes to the growth of hepatocellular carcinoma. Therefore, based on the available literature data and the results of the present study, serum B cell activating factor contributes to early patient severity of COVID-19 and may be a good predictive marker for the disease prognosis. Diagnostic Performance of Serum CALP and BAFF in COVID-19 Patients Due to the non-significantly increased blood levels of CALP and BAFF found in COVID-19 patients in the present study, the ability of blood CALP and BAFF to predict COVID-19 was assessed using the ROC curves. According to a presentation by Chen et al.,18 extremely high levels of Calprotectin were con- nected to the poor overall survival of COVID-19 patients, sup- porting the predictability of Calprotectin revealed by earlier investigations. Recent studies by Shi et al.13 and Zuo et al.,15 and others13,15 demonstrated high serum Calprotectin is closely connected to the likelihood of dying in COVID-19, usually from thrombotic problems, which lends credence to the ver- dicts of the current study. Calprotectin is said to have a higher predictive accuracy when compared to the COVID-GRAM risk score created for prediction by Liang et al.45 and Chen et al.18 Calprotectin was thought to have the highest prediction accuracy of all the predictors, according to Chen et al.18 They examined the receiver operating characteristic curve (ROC) analysis of Calprotectin, HMGB1, COVID-GRAM risk score, and Calprotectin/HMGB1 combo for predicting ICU admis- sion and possible mortality to illustrate results similar to the present investigation. Conclusion This study is the first to demonstrate that COVID-19 patients had greater serum levels of the potent inflammatory markers CALP, BAFF, and CRP. The clinical illness condition of to a recent investigation, people with confirmed SARS-CoV-2 infection exhibited increased plasma Calprotectin levels com- pared to suspected patients with negative RT-PCR.17 Numerous researchers have confirmed the role of Calprotectin in evalu- ating illness severity, including studies by Chen et al.,18 Kaya et al.,19 Garcia de Guadiana-Romualdo et al.,1 Mahler et al.,20 and Bauer et al.21 Neutrophils are crucial to the immunopathology of COVID-19, according to a recent study by Tomar et al.22 As a result, it has been discovered that measuring blood Calpro- tectin levels is a trustworthy indication of COVID-19 severity. Studies proved that neutrophils mainly secrete Calprotectin in response to inflammation. Recently, it was shown that Calpro- tectin is a biomarker of inflammation that can be used to track the progression of numerous inflammatory diseases.23–28 Lim- ited research studies look at the connection between the severity and predicator value of serum Calprotectin in COVID-19. Patients brought to the ICU had significantly higher serum levels of Calprotectin than non-ICU patients, and those who died had much higher levels, according to Chen et al.,18 who conducted a study with 121 COVID-19 patients (41 ICU, 81 non-ICU). Additionally, that study discovered a correlation between higher mortality in COVID-19 patients with a substantial rise in serum Calprotectin. In their trial with 94 COVID-19 patients, Shi et al. study found that patients needing mechan- ical breathing had higher serum Calprotectin levels than those not.13 Based on the available literature and the present study results, we can conclude that serum Calprotectin may be employed as a predictive biomarker for COVID-19 disease severity and prognosis. Serum Level of B Cell Activating Factor The greater B-cell activation in COVID-19 patients may be responsible for the many autoantibodies and immune com- plexes frequently found in these individuals’ blood. Our research offered the first conclusive evidence that circulating BAFF levels in COVID-19 patients were higher than in healthy controls. These findings suggest that BAFF participates in per- sistent viral infection and aids in disease progression. Specifi- cally, BAFF impacts B cell development, maturation, survival, and activation.29,30 Studies have shown that the process of viral infection caused by COVID-19 and others induces contact between T cells and activated B cells with T cells.31-33 Moreover, it has been shown that viral infections, including infections with the respiratory syncytial virus, might cause BAFF release.34,35 Consequently, even though the fundamental mechanisms may change, it is believed that BAFF is frequently produced by viral infection.36 According to previous research, our findings provide new evidence that COVID-19 infection may induce the biosynthesis and release of BAFF, which may affect how B cells react to viral infection. The Tumor Necrosis Factor family member B-cell activating factor (BAFF), also known as B lymphocyte stimulator (BLyS) or B cell activating factor, has a unique role in regulating peripheral B-cell sur- vival, homeostasis, and the antibody response.29,37 Its believed that BAFF could reduce apoptosis and essentially enhances T cell-independent and T cell-dependent humoral immune responses. The study led by Sutherland et al.38 found that BAFF increased T- and B-cell responses, particularly Th1-type responses. Numerous cells, particularly those connected to the immuno-inflammatory response, such as monocytes, mac- rophages, neutrophils, dendritic cells (DCs), T lymphocytes, 125J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 H.M. Balaky et al. Original Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients COVID-19 and increased BAFF levels are correlated. The SARS-COV-2 infection risk and severity correlated with serum CALP and BAFF levels. The study results suggest a con- nection between serum BAFF levels and the manifestation of COVID-19, and assessing serum BAFF levels may be used as an inflammatory biomarker to identify and classify clinical problems related to COVID-19. According to the available evidence, Calprotectin may be a valuable inflammatory bio- marker to evaluate the risk and severity of COVID-19. The relationship between Calprotectin and the inflammatory pro- cess may present fresh opportunities for managing and improving COVID-19. The combined use of serum CALP, BAFF and CRP levels may be helpful to evaluate and under- stand how inflammation-related factors such as viral load, SARS-CoV2 antibodies, corticosteroid use, anticoagulants, and pharmaceutical agents would affect neutrophil function. A comprehensive prospective investigation is required to com- prehend the progression of the COVID-19 infection, the potential role of blood BAFF levels in determining and moni- toring the condition’s prognosis, and the treatment response to immunomodulatory medicine. Additional study is also required to completely comprehend the roles played by BAFF in the emergence of COVID-19-associated diseases and the development of the infection. Conflict of Interest All authors declare that they have no conflicts of interest.  References 1. García de Guadiana-Romualdo, L. et al. Circulating levels of Calprotectin, a signature of neutrophil activation in prediction of severe respiratory failure in COVID-19 patients: a multicenter, prospective study (CalCov study). Inflammation Research 71, 57–67 (2022). 2. Guan, W.-j. et al. Clinical characteristics of coronavirus disease 2019 in China. New England Journal of Medicine 382, 1708–1720 (2020). 3. Machhi, J. et al. The natural history, pathobiology, and clinical manifestations of SARS-CoV-2 infections. Journal of Neuroimmune Pharmacology 15, 359–386 (2020). 4. Chang, S. E. et al. New-onset IgG autoantibodies in hospitalized patients with COVID-19. Nature Communications 12, 1–15 (2021). 5. van Kampen, J. J. et al. Duration and key determinants of infectious virus shedding in hospitalized patients with coronavirus disease-2019 (COVID-19). Nature Communications 12, 1–6 (2021). 6. Ortega, N. et al. Seven-month kinetics of SARS-CoV-2 antibodies and role of pre-existing antibodies to human coronaviruses. Nature Communications 12, 1–10 (2021). 7. Udeh, R., Advani, S., de Guadiana Romualdo, L. G. & Dolja-Gore, X. Calprotectin, an emerging biomarker of interest in COVID-19: a systematic review and meta-analysis. Journal of Clinical Medicine 10, 775 (2021). 8. Silvin, A. et al. Elevated calprotectin and abnormal myeloid cell subsets discriminate severe from mild COVID-19. Cell 182, 1401–1418. e1418 (2020). 9. Jukic, A., Bakiri, L., Wagner, E. F., Tilg, H. & Adolph, T. E. Calprotectin: from Biomarker to Biological Function. Gut 70, 1978–1988 (2021). 10. Wang, L. et al. B cell activating factor regulates periodontitis development by suppressing inflammatory responses in macrophages. BMC Oral Health 21, 1–15 (2021). 11. Yang, S.-C., Tsai, Y.-F., Pan, Y.-L. & Hwang, T.-L. Understanding the role of neutrophils in acute respiratory distress syndrome. Biomedical Journal 44, 439–446 (2021). 12. Veras, F. P. et al. SARS-CoV-2–triggered neutrophil extracellular traps mediate COVID-19 pathology. Journal of Experimental Medicine 217 (2020). 13. Shi, H. et al. Neutrophil calprotectin identifies severe pulmonary disease in COVID‐19. Journal of Leukocyte Biology 109, 67–72 (2021). 14. Nascimento, M. et al. B-cell activating factor secreted by neutrophils is a critical player in lung inflammation to cigarette smoke exposure. Frontiers in Immunology 11, 1622 (2020). 15. Zuo, Y. et al. Neutrophil extracellular traps in COVID-19. JCI insight 5 (2020). 16. Hanssen, N. M., Spaetgens, B., Nagareddy, P. R. & Murphy, A. J. DAM Pening mortality in COVID-19: therapeutic insights from basic cardiometabolic studies on S100A8/A9. Circulation 143, 971–973 (2021). 17. Cherubini, F., Cristiano, A., Valentini, A., Bernardini, S. & Nuccetelli, M. Circulating Calprotectin as a supporting inflammatory marker in discriminating SARS-CoV-2 infection: an observational study. Inflammation Research 70, 687–694 (2021). 18. Chen, L. et al. Elevated serum levels of S100A8/A9 and HMGB1 at hospital admission are correlated with inferior clinical outcomes in COVID-19 patients. Cellular & Molecular Immunology 17, 992–994 (2020). 19. Kaya, T. et al. Serum calprotectin as a novel biomarker for severity of COVID-19 disease. Irish Journal of Medical Science (1971-) 191, 59–64 (2022). 20. Mahler, M., Meroni, P.-L., Infantino, M., Buhler, K. A. & Fritzler, M. J. Circulating calprotectin as a biomarker of COVID-19 severity. Expert Review of Clinical Immunology 17, 431–443 (2021). 21. Bauer, W. et al. Outcome prediction by serum calprotectin in patients with COVID-19 in the emergency department. Journal of Infection 82, 84–123 (2021). 22. Tomar, B., Anders, H.-J., Desai, J. & Mulay, S. R. Neutrophils and neutrophil extracellular traps drive necroinflammation in COVID-19. Cells 9, 1383 (2020). 23. Romand, X. et al. Systemic Calprotectin and chronic inflammatory rheumatic diseases. Joint Bone Spine 86, 691–698 (2019). 24. Wirtz, T. H. et al. Association of serum calprotectin concentrations with mortality in critically ill and septic patients. Diagnostics 10, 990 (2020). 25. Kunutsor, S. K. et al. Plasma calprotectin and risk of cardiovascular disease: Findings from the PREVEND prospective cohort study. Atherosclerosis 275, 205–213 (2018). 26. Wang, Q., Chen, W. & Lin, J. The Role of Calprotectin in rheumatoid arthritis. Journal of Translational Internal Medicine 7, 126–131 (2019). 27. Yurtsever Kum, N. et al. Elevated serum calprotectin as an inflammatory marker in obstructive sleep apnea. CRANIO®, 1–7 (2020). 28. Candar, T., Baklacı, D., Kuzucu, İ. & Kayabaşı, S. A proinflammatory marker in chronic rhinosinusitis: serum calprotectin. Acta Biochimica Polonica (2020). 29. Do, R. K. G. & Chen-Kiang, S. Mechanism of BLyS action in B cell immunity. Cytokine & Growth Factor Reviews 13, 19–25 (2002). 30. Schneider, P. & Tschopp, J. BAFF and the regulation of B cell survival. Immunology Letters 88, 57–62 (2003). 31. Oliviero, B. et al. Enhanced B-cell differentiation and reduced proliferative capacity in chronic hepatitis C and chronic hepatitis B virus infections. Journal of Hepatology 55, 53–60 (2011). 32. Das, A. et al. IL-10–producing regulatory B cells in the pathogenesis of chronic hepatitis B virus infection. The Journal of Immunology 189, 3925–3935 (2012). 33. Wang, K. et al. Overexpression of Fc receptor-like 1 associated with B-cell activation during hepatitis B virus infection. Brazilian Journal of Medical and Biological Research 45, 1112–1118 (2012). 34. Toubi, E. et al. Elevated serum B-Lymphocyte activating factor (BAFF) in chronic hepatitis C virus infection: association with autoimmunity. Journal of Autoimmunity 27, 134–139 (2006). 35. McNamara, P. et al. Respiratory syncytial virus infection of airway epithelial cells, in vivo and in vitro, supports pulmonary antibody responses by inducing expression of the B cell differentiation factor BAFF. Thorax 68, 76–81 (2013). 36. Ittah, M. et al. Induction of B cell-activating factor by viral infection is a general phenomenon, but the types of viruses and mechanisms depend on cell type. Journal of Innate Immunity 3, 200–207 (2011). 37. Rahman, Z. S. & Manser, T. B cells expressing Bcl-2 and a signaling-impaired BAFF-specific receptor fail to mature and are deficient in the formation of lymphoid follicles and germinal centers. The Journal of Immunology 173, 6179–6188 (2004). 38. Sutherland, A. P. et al. BAFF augments certain Th1-associated inflammatory responses. The Journal of Immunology 174, 5537–5544 (2005). 39. Nardelli, B. et al. Synthesis and release of B-lymphocyte stimulator from myeloid cells. Blood, The Journal of the American Society of Hematology 97, 198–204 (2001). 126 J Contemp Med Sci | Vol. 9, No. 2, March-April 2023: 121–126 Physiological Effects of Calprotectin and B Cell Activating Factor in COVID-19 Patients Original H.M. Balaky et al. 40. Scapini, P. et al. G-CSF–stimulated neutrophils are a prominent source of functional BLyS. The Journal of Experimental Medicine 197, 297–302 (2003). 41. Zhu, J. et al. BlyS is up-regulated by hypoxia and promotes migration of human breast cancer cells. Journal of Experimental & Clinical Cancer Research 31, 1–7 (2012). 42. Jablonska, E. et al. Overexpression of B cell-activating factor (BAFF) in neutrophils of oral cavity cancer patients—preliminary study. Neoplasma 58, 211 (2011). 43. Fragioudaki, M. et al. Serum BAFF levels are related to angiogenesis and prognosis in patients with multiple myeloma. Leukemia Research 36, 1004–1008 (2012). 44. Koizumi, M. et al. Increased B cell-activating factor promotes tumor invasion and metastasis in human pancreatic cancer. PloS One 8, e71367 (2013). 45. Liang, W. et al. Development and validation of a clinical risk score to predict the occurrence of critical illness in hospitalized patients with COVID-19. JAMA Internal Medicine 180, 1081–1089 (2020). This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly. https://doi.org/10.22317/jcms.v9i2.1327