Lymphocytes and B-cell abnormalities in patients with common variable immunodeficiency (CVID)

Background and aims: Common variable immunodeficiency (CVID) is a primary antibody deficiency characterised by decreased antibody production and low or normal B-cell numbers. To elucidate the clinical and immunological heterogeneity of CVID, we studied 16 patients diagnosed with CVID. Methods: We analysed B, T and NK cell populations. We also assessed CD27 expression to define B-cell subsets and examined the expression of molecules important in B-cell proliferation and differentiation, such as the transmembrane activator and CALM interactor (TACI), inducible costimulator (ICOS), CD154 and CD40. Results: We observed reduced B and T-cell numbers in CVID patients; this reduction was more pronounced in adults. While one group of patients (group I) showed a significant reduction in CD27+ memory B-cells, another group (group II) of patients exhibited numbers of CD27+ memory B-cells similar to the healthy donor. The frequency of B-cells and T-cells expressing CD40 and ICOS, respectively, was significantly lower in all CVID patients compared with healthy donors. Finally, a correlation between the frequency of CD27+ memory B-cells and clinical features was observed in CVID patients. Conclusion: These results suggest that in some patients, the combined defects in both T and B-cells may account for CVID. Additionally, patients in group I exhibited an increased frequency of pneumonia and chronic diarrhoea.