In vitro IgM and IgM rheumatoid factor production in response to Staphylococcus aureus Cowan I and pokeweed mitogen: the contribution of CD5+ (Leu 1) B cells.

The relation between the percentage of circulating CD5+ CD20+ B cells and the ability to synthesize IgM and IgM rheumatoid factor (RF) in vitro in response to pokeweed mitogen (PWM) and Staphylococcus aureus Cowan I (SAC) was assessed in 21 healthy controls. CD5+ CD20+ cells ranged from 7.3 to 19.9% of total CD20+ B cells. By Spearman's rank correlation, there was an inverse relation between the percentage of CD5+ CD20+ B cells and IgM production in response to PWM (rs = -0.452, p less than 0.05) and a direct correlation with RF production in response to SAC (rs = 0.450, P less than 0.05). The percentage of CD5+ CD20+ B cells was not related to any serologic HLA-A, B, C or D antigen. Healthy individuals may be predisposed to producing IgM or autoantibodies based on the percentage of circulating CD5+ Cd20+ B cells.