Characteristics of suppressor factors generated from human mononuclear cells using concanavalin A and C-reactive protein.

Lymphocytes from normal human donors were cultured in Marbrook flasks in the presence of C-reactive protein (CRP), concanavalin A (Con A) or serum amyloid A protein low molecular weight component (SAAL) and the culture supernatants were tested for their ability to suppress the pokeweed mitogen (PWM) driven response of normal human lymphocytes. The supernatants from CRP and Con A stimulated lymphocytes, when added to cultures at initiation at a final concentration of 5%, suppressed the plaque forming cell (PFC) response in the three major immunoglobulin (Ig) classes. The suppressive effect could be removed by absorption of the culture supernatants with lentil lectin and with antisera to antigen specific helper and suppressor factors and could be recovered in the eluate. The results indicate that CRP stimulated cells exert their suppressive effect through a soluble mediator(s) which is similar to Con A generated suppressor factor(s) in respect to its time of action, its effect on the Ig classes M, G and A, its lack of cytoxicity and some structural aspects.