Potential Role of Immune System and Its Cells against (SARS -COV-2) and COVID 19

coronavirus disease-2019 (COVID-19) is a novel pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV2). It presents with wide variations in disease severity, and certain populations appear to be more susceptible than others. The mechanisms of such heterogeneity in disease presentation and susceptibility are largely unclear, and this review article aims to examine the existing evidence for the involvement of the human Major Histocompatibility Complex (MHC) system, which is also known as the Human Leukocyte Antigen (HLA) system, as potential effectors of such heterogeneity. We critically examined in-silico studies, and classified HLA class 1 and 2 alleles into risk and protective alleles based on existing evidence. Furthermore, we summarized the relationship between HLA-DR expression and COVID-19 pathophysiology based on functional studies. We postulate that the identification of HLA alleles that confer risk or protection for COVID19 will not only shed light on understanding disease epidemiology but will also help to guide vaccine development and predict vaccine efficacy across populations.