C-reactive protein reduces the promotion of human B-cell colony formation by autoreactive T4 cells and T-cell proliferation during the autologous mixed-lymphocyte reaction.

Utilizing a dual liquid/semisolid culture system with human B cells suspended in a semisolid matrix, T4 helper cells activated in the autologous mixed-lymphocyte reaction (AMLR) were much more effective than T8 suppressor cells in promoting B-cell colony formation in the presence of Staph protein A. C-reactive protein (CRP) inhibited the promotion of B-cell colony formation by autoactivated T cells and inhibition was observed only when CRP was present during the early AMLR. Coculture experiments revealed that CRP directly reduced T4 promotion of colony formation rather than inducing T8-mediated suppression of T4 cells. B cells preincubated with CRP responded normally to facilitative signals from autoactivated T cells; however, monocytes or T cells preincubated with CRP were reduced in AMLR promotion of colony formation. Other results indicated that CRP inhibition of colony formation during the AMLR was associated with considerable reductions in the proliferation of autoreactive T cells. These data demonstrate that CRP can directly reduce the ability of autoreactive T4 cells to expand the B-cell compartment and that CRP blocks T-cell activation events proximal to proliferation.