The Study of AID Gene Expression in B Lymphocytes from CVID Patients

Common variable immunodeficiency (CVID) is one of the most frequent cases of primary immunodeficiency. It is likely that this heterogeneous disease is caused by several distinct genetic disorders. The activation-induced cytidine deaminase (AID) enzyme is involved in class switching, somatic hypermutation (SHM) and processes associated with gene conversion in the germinal center. In order to clarify the possible role of AID in the pathogenesis of CVID, we have studied the AID gene expression in CVID patients. Peripheral blood mononuclear cells (PBMC) from 21 patients and healthy controls were isolated. The isolated cells were stimulated by CD40L and IL-4 to induce AID gene expression. After five days, total RNA from the stimulated cells was extracted and AID gene expression was investigated by RT-PCR. RT-PCR results showed that after stimulation by CD-40L and IL-4, the AID gene was expressed in all of the samples. The control samples were also positive for AID gene mRNA expression. In this investigation we studied the expression of AID gene in CVID patient's B lymphocytes for the first time. Regards to our results which showed that all patients normally expressed the AID gene mRNA and considering that one of the main problems in a number of CVID patients is disorders in phenomena related to the germinal center and complete differentiation of B lymphocytes, it can be concluded that possible defects in other molecules involved in class switching is responsible for this disease. Understanding the various genetic defects responsible for this heterogeneous disease could lead to its division into more homogenous subtypes with distinct therapeutic strategies, so further investigations is recommended.