Differential proliferative responses of B cells from BALB/c and autoimmune NZB mice to B-cell growth factor(s).

Highly purified B cells from NZB mice have altered responses to various stimuli which require additional costimulatory signals supplied by factors present in EL-4 supernatants when compared to age-matched control nonautoimmune strains. Both crude preparations of EL-4 supernatants as well as partially purified BSF-p1 induced peak proliferation in B cells from normal strains of mice only in the presence of another stimulatory signal, anti-mu. In contrast, B cells from autoimmune-prone NZB mice proliferated in response to B-cell growth factors, with an age-dependent variation. Splenic B cells from 16- to 22-week-old NZB mice, an age where pronounced autoimmune disease is not observed, demonstrated a near maximum proliferative response with B-cell growth factors alone. While normal B cells responded maximally to BSF-p1 in the presence of anti-mu, B cells from young adult NZB mice (16-22 weeks of age) were not further stimulated to proliferate upon the addition of anti-mu. Such NZB B cells appeared to lack the requirement for a stimulation signal delivered by anti-mu in order to respond to B-cell growth factors. These results suggested that NZB cells were partially activated in vivo in the preautoimmune state so that subliminal triggers lead to full activation.