C-reactive protein- (CRP) mediated modulation of human B cell colony development

The ability of human C-reactive protein (CRP) to modulate Staph protein A-(SpA) induced human B cell colony formation in semisolid cultures was investigated. Maximal augmentation was observed with 10 and 25 micrograms/ml CRP and was independent of the SpA concentration used to stimulate colony formation. Optimal facilitation of colony numbers was noted when CRP was present during the initial stages of colony formation and the facilitation represented an early increase in colony numbers. At later incubation intervals, however, the colony responses of cultures containing 25 and 50 micrograms/ml CRP were considerably diminished when compared to controls that appeared secondary to the focal disintegration of colony clusters rather than the actual suppression of certain colony progenitors with delayed colony-forming kinetics. Other experiments showed the 18-hr pre-exposure of cells to CRP facilitated colony formation, and that after preincubation, a small frequency of CRP binding cells could be detected by flow microcytofluorometry. Therefore, these studies indicate that a possible biologic function of CRP is the ability to modulate the activities of the B cell system.