Phenotypic and functional heterogeneity of human T lymphocytes producing B-cell growth factor(s): A clonal analysis

Human T cells active on B-cell proliferation are phenotypically and functionally heterogeneous. A series of 43 human T-cell clones, selected according to their ability to release factors active on B-cell proliferation, were analyzed. B-Cell proliferation was evaluated by two different assays, namely, a costimulation assay with anti-μ antibody or by an assay based on B-cell preactivation with Staphylococcus aureus. Eight of these clones expressed the T4^- T8⁺ phenotype while the remaining were T4⁺ T8^-. The large majority had T-cell growth factor activity as well. However, some clones appeared to have B-cell growth factor activity only. Fourteen clones (eight T8⁺ and six T4⁺) also displayed cytolytic activity in a phytohemagglutinin-dependent cytolytic assay.