Expression of Pax5 gene in human haematopoietic cells and tissues: comparison with immunodeficient donors.

In mice, Pax5 gene is indispensable for B cell development. Pax5-deficient mice fail to produce mature B cells owing to complete arrest of B cell development at a precursor stage. However, the lineage and stage of human Pax5 gene expression have remained elusive. In this investigation expression of the human Pax5 gene was studied. Pax5 gene expression was detected in B cell lines but not in myeloma cell lines. CD19 expression was correlated with Pax5 gene expression. Adult spleen and bone marrow and fetal spleen and liver showed strong Pax5 gene expression, as did the corresponding mouse tissues, as reported previously. In common variable immunodeficiency (CVID) peripheral blood lymphocytes (PBL) with a decreased number of B cells, no Pax5 gene expression was detected. Some CVID PBL stimulated with IL-2, IL-10 and anti-CD40 monoclonal antibody, expressed the Pax5 gene. Defect of Pax5 gene expression in CVID may be caused by regulatory T cell disorder.