In vitro IgG rheumatoid factor production by CD5-negative murine B cells in response to immune complexes of lipopolysaccharide

Abstract

SUMMARY We studied the in vitro production of rheumatoid factor (RF) by spleen cells of normal adult mice. IgG RF cross-reactive with rabbit IgG was produced in response to immune complexes of TNP-lipopolysaccharide (LPS) with murine IgG anti-TNP antibody in an Fc-specific manner, but not to a mixture or IgG and LPS. Antibody-uncomplexed LPS induced little IgG RF production, but suppressed the subsequent IgG RF response to antibody-complexed LPS, whereas IgM RF was induced by either LPS or antibody-complexed LPS. The IgG RF production followed as rapid a time course as IgM RF production; the rate of IgG RF production reached its maximum soon after a lag period of l day and declined after S days. Treatment of splenic B cells from BALBJc mice with anti-Ly-1.2 antibody and rabbit complement resulted in a selective reduction of IgM RF production by 90%, with little effect on IgG RF production. These result suggest that IgG RF is derived primarily from CDS memory B cells which have been developed in normal mice by an unknown mechanism. Unlike the CT)5+ precursor cells for IgM RF, these memory cells arc unresponsive to polyclonal stimulation by LPS but are activated by simultaneous stimulation by aggregated He epilopes and the mitogenic stimulus from LPS.