[49] observed increased in CD8+ TEMRA in severe cases, whereas we observed increase in the CVID patient who had a moderate course of COVID-19. and the CVID patient. A marked decrease in GC B cells and plasmablasts may be responsible for failure to make SARS-CoV-2 antibodies. The lack of SARS-CoV-2 antibodies with moderate clinical disease suggests an important role of T-cell response in defense against SARS-CoV-2 contamination. Keywords: Memory T and B cells, Follicular helper T cells, Regulatory lymphocytes, Plasmablasts, Germinal center B cells Introduction SARS-CoV-2 contamination (COVID-19) is usually pandemic with >95 million individuals infected, >300,000 new cases each day, and >1 million deaths worldwide. Following SARS-CoV-2 contamination, >80% of individuals are asymptomatic or have moderate disease [1]. However, 5C10% patients suffer with serious disease and another 5C10% with crucial disease requiring admission to intensive care models and life-support Atenolol steps with a high mortality rate. The serious disease appears to be, at least in part, due to cytokine storm contributed predominantly by innate immune responses [2, 3]. However, adaptive immune responses may contribute to clinical outcomes and severity of disease in a majority of infected individuals. Both antibody and T-cell responses have been analyzed in patients with CO-VID-19; however, most of these studies have been reported in severe disease and recovered patients, and very limited data are available for moderate disease [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]. A number of changes in CD4+ T cell and CD8+ T cell number and functions, including CD4+ and CD8+ T cell lymphopenia, presence of activated T cells, increased or reduced worn out T cells, dysregulated immune responses, and impaired cytotoxic responses, have been reported [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17]; however, the role of T cells in moderate disease and asymptomatic subjects is poorly comprehended. Following antigenic activation, na?ve CD4+ and CD8+ T cells (TN) undergo activation and clonal growth to generate effector CD4+ and CD8+ T cells. This clonal growth phase is followed by a phase of contraction due to apoptosis of effector T cells. A subpopulation of effectors cells is usually retained as long-term memory cells. Based upon their homing properties, and expression of adhesion molecules and chemokine receptors, memory T cells are classified into central memory (TCM) and effector memory (TEM) CD4+ and CD8+ T cells [18, 19, 20, 21, 22, 23, 24, 25, 26]. A small populace of TEM cells reacquires CD45RA and is termed as terminally differentiated effector memory T cells (TEMRA). These subsets differ with regard to proliferative response, cytokine production, effector properties, and sensitivity to apoptosis [27, 28, 29]. Much like T cells, the role of antibodies in the pathogenesis and clinical end result in COVID-19 is not well understood. The majority of patients develop COVID-19 antibodies 1C2 weeks following SARS-CoV-2 contamination, and increased circulating plasma cells have been reported [14, 30, 31, 32, 33]. B-cell development initiates in the bone marrow from common lymphoid progenitors and undergo activation, proliferation, and differentiation in the lymph nodes and spleen [34, 35, 36]. Immature B cells leave the bone marrow as transitional B cells. Transitional cells represent a crucial step in the differentiation and selection of the mature B-cell compartment. Transitional B cells migrate to lymphoid follicles and a minor population to the marginal zone. In the follicle, antigen binding to the B-cell receptor activates B cells. Antigen-activated B cells interact with follicular helper T (TFH) cells, where they undergo proliferation and form germinal centers (GCs). In the GCs, B cells undergo immunoglobulin class-switch recombination and selection of high-affinity B cells. Subsequently, B Atenolol cells leave the GCs to differentiate into long-lived plasma cells homing into the bone marrow to produce antibodies of different isotypes. A small populace of GC B cells leaves the GCs to become class-switched memory (CSM) B cells. The Atenolol marginal zone (MZ) B cells after interacting with antigens differentiate into short-lived antibody-secreting plasma plasmablasts [37], and a FA-H small population is retained as IgM memory B cells. IgM memory B cells, after interacting with antigen, undergo proliferation and differentiation to plasmablasts [38]. In this study, we present a comprehensive analysis of various subsets of CD4+ and CD8+ T cells, subsets of B cells, and regulatory lymphocytes in an immunocompetent patient and a patient with common variable immunodeficiency disease (CVID) with moderate.