Both splenic CD5(+) B and CD5(-) B cells produce platelet glycoprotein-specific autoantibodies in chronic ITP

The objective of the present study is to determine splenic B-cell subsets and the ability of splenic CD5(+) B and CD5(-) B cells to produce platelet glycoprotein-specific autoantibodies in chronic idiopathic thrombocytopenic purpura (ITP). Splenic CD5(+) B cells were identified by two-color flow cytometric analysis in eight ITP patients. Magnetic activated cell sorting (MACS) purified splenic CD5(+) B cells and CD5(-) B cells were cultured separately in vitro. Glycoprotein-specific autoantibodies in culture supernatants and plasma were measured by modified monoclonal antibody immobilization of platelet antigen (MAIPA) assay. The percentage of splenic CD5(+) B cells in ITP patients was slightly higher than that in controls, with no statistical significance. Four ITP patients displayed plasma IgG autoantibodies against both GPIIb/IIIa and GPIb. Moreover, splenic CD5(+) B cells and CD5(-) B cells from these four ITP patients also produced high level of IgG anti-GPII(b)/III(a) and anti-GPI(b) antibodies. However, we were unable to detect IgM GP-specific autoantibodies in culture supernatant and plasma in these ITP patients. It is concluded that both splenic CD5(+) B cells and CD5(-) B cells produce platelet IgG GP-specific autoantibodies, and may all play a role in the pathogenic process of ITP.