Peripheral B-lymphocyte markers and function in IgA nephropathy.

Peripheral blood B-lymphocyte markers and functions were observed in 21 patients with IgA nephropathy (IgA NP) and in 16 controls. IgA NP B lymphocytes expressed significantly higher positivity with Leu 1 (CD 5) monoclonal antibody than controls. CD 5 positive B lymphocytes are thought to be a distinct subset of the B cells (autoregulatory B lymphocytes) inducible in IgA NP by lipopolysaccharide (LPS) stimulation parallel to the higher expression of surface IgM heavy chain positivity. The activated state of IgA NP B lymphocytes has been proved by their higher OKIa (HLA-DR) positivities but lower IOB1a (CD 21, C3d-receptor) and decreased IgG-Fc-receptor (ox-rosette) expression. IgA NP B lymphocytes showed a higher IgA but also IgG and IgM polyclonal immunoglobulin production than control B lymphocytes in co-cultures with T lymphocytes. Not only regulatory T lymphocyte subsets but also serum derived from IgA NP patients stimulated the immunoglobulin production of IgA NP B cells.