Objective To investigate the quantities of bone marrow CD5+ B lymphocytes in the patients with autoimmune hemocytopenia and the relationship between quantities of CD5+ B lymphocytes and clinical or laboratorial parameters. Methods Quantities of CD5+ B lymphocytes in the bone marrow of 14 patients with autoimmune hemolytic anemia （AIHA） or Evans syndrome

22 immunorelated pancytopenia （IRP） patients

and 10 normal controls were assayed by flow cytometry. The correlation between their clinical or laboratorial parameters and CD5+ B lymphocytes was analyzed. Results The quantity of CD5+ B lymphocytes of AIHA/Evans syndrome （34.64%±19.81%） or IRP patients （35.81%±16.83%） was significantly higher than that of normal controls （12.00%±1.97%

P<0.05）. However

there was no significant difference between AIHA/Evans syndrome and IRP patients （P>0.05）. In all hemocytopenic patients

the quantity of bone marrow CD5+ B lymphocytes showed significantly negative correlation with serum complement C3 level （r=-0.416

P<0.05）. In the patients with AIHA/Evans syndrome

the quantity of bone marrow CD5+ B lymphocytes showed significantly positive correlation with serum indirect bilirubin level （r=1.00

P<0.05）. In Evans syndrome patients

the quantity of CD5+ B lymphocytes in bone marrow showed significantly positive correlation with platelet-associated immunoglobulin G （r=0.761

P<0.05） and platelet-associated immunoglobulin M （r=0.925

P<0.05）. The quantity of CD5+ B lymphocytes in bone marrow of all hemocytopenic patients showed significantly negative correlation with treatment response （tau-b=-0.289

P<0.05）

but had no correlation with colony forming unit-erythroid （r=-0.205

P>0.05） or colony forming unit-granulocyte-macrophage colonies （r=-0.214

P>0.05）. Conclusions The quantity of bone marrow CD5+ B lymphocytes in the patients with autoimmune hemocytopenia significantly increases and is correlated with disease severity and clinical response

which suggest that CD5+ B lymphocytes might play an important role in the pathogenesis of autoimmune hemocytopenia.