Heterogeneity of B cell growth factor (BCGF)-producing T cells in humans. Clonal analysis of BCGF-producing cells within T4+ and T8+ subsets and evidence for the involvement of different growth factors in different BCGF assays.

Human peripheral blood T cells were cloned under conditions allowing the clonal expansion of virtually all T cells. Clones derived from T4+ or T4- (T8+) subsets were screened for their ability to induce B cell proliferation either in the Staphylococcus aureus Cowan-I (SAC)-driven assay or in the costimulation assay based on the use of anti-mu antibodies. BCGF activity in the SAC- and in the anti-mu-driven system was displayed by 13% and 15% T8+ clones, respectively, while 74% and 79% T4+ clones had BCGF activity in the same assay. SN of clones with BCGF activity were further screened for their susceptibility to the inhibition by CM 269 (anti-IL-2 receptor) monoclonal antibody. All clones were inhibited in the SAC assay, whereas several clones were partially or totally resistant to inhibition in the anti-mu assay. Nine of such non-inhibited clones were further analyzed for their ability to produce gamma-IFN (known to act as a BCGF) and IL-2: six of them were found to produce gamma-IFN, while none produced any detectable IL-2 activity.