Background: Common Variable Immunodeficiency (CVID) is a heterogeneous disorder characterized by defective antibody production and differentiation of B cells. The proliferation of B cells is an essential step for antibody synthesis. Depending on the nature of the stimulus their response may be T cell-dependent or T cell-independent. Methods: We worked with 23 CVID patients and 14 healthy donors (HD), the patients were divided by their percentage of memory B cells. Apart from standard immunophenotyping of circulating human B and T cell subsets, an in vitro CFSE dilution assay was used for the assessment of proliferative capacity in B cells and comparing the activation of the T cell-dependent and T cell-independent response in the patients. Results: Patients with a reduction in their memory B cells; have an increase in follicular T cells(Tfh) cells as well as a low proliferation with the PKW, CpG, and SAC stimuli (p= 0.022; p= 0.0073, respectively); while the patients with a normal percentage of memory B cells showed a high expression of IL-21R, such as low proliferation before only CPG and with IL-21, CD40L and anti-IgM stimuli (p= 0.0473, p= 0.0163 and p = 0.0475, respectively). Conclusion: Defective proliferation in patients depends on the type of stimulus used and the phenotypic characteristics of the patients. Further study is necessary to understand disease mechanisms, that can guide us to genetic defects in CVID.