Investigation of the correlation between clinic, immunologic and genetic features with B cell subgroup characteristics and KREC levels of common variable immunodeficiency patients

Common variable immunodeficiency (CVID) is a heterogeneous group of primary antibody deficiencies characterized by recurrent infections and poor response to vaccines with defects in B cell differentiation and antibody production. In recent years, attempts have been made to classify CVID based on immunophenotyping of B cell populations. Real-time quantitative polymerase chain reaction (RT-qPCR) for quantification of Kappa-Deleting Recombination Excision Circles (KRECs) is used for neonatal screening of B cell immunodeficiencies. KRECs are episomal DNA fragments that occur during V(D)J rearrangement of B cell receptor (BCR) genes in bone marrow. 30 patients diagnosed with CVID in Section of Pediatric Immunology, Hacettepe University, İhsan Doğramacı Children's Hospital were included in this study. B cell subgroups of CVID patients were evaluated by flow cytometry, KREC levels of the patients were measured with RT-qPCR and evaluated in comparison with 41 healthy controls. The mean age of the patients was 28,5±15.6 years. The distribution between the genders was 1:1. 33% of patients have consanguineous parents. The most common complaint of admission was frequent infection. There were 6 patients (20%) with normal IgM levels and 2 patients (6.67%) with normal IgA levels. CD19+ cell counts were low in 20 patients (66.67%) while 14 patients (46.67%) had low CD4+ cell numbers. There was a decrease in the number of B cells of the controls with the increasing age (p<0.01). Transitional B cells and naive B cells were inversely correlated with age (p<0.01). KREC levels were not different between genders. However, KREC level was inversely correlated with age only in healthy controls (p<0.01). Total B cell numbers were positively correlated with KREC levels of patients and controls (p<0.01). In the study, B cell subgroup numbers and KREC levels in the normal population in our unit were obtained according to age. Evaluation of the inverse correlation between B cells/KREC levels and age of contols may also be important in terms of demonstration of immune aging. Keywords: CVID, B cell, KREC, RT-qPCR, flow cytometry