CD40 ligand‐positive CD8+T cell clones allow B cell growth and differentiation

摘要

AbstractA fraction of activated CD8+T cells expresses CD40 ligand (CD40L), a molecule that plays a key role in T cell‐dependent B cell stimulation. CD8+T cell clones were examined for CD40L expression and for their capacity to allow the growth and differentiation of B cells, upon activation with immobilized anti‐CD3. According to CD40L expression, CD8+clones could be grouped into three subsets. CD8+T cell clones expressing high levels of CD40L (≥80 CD40L+cells) were equivalent to CD4+T cell clones with regard to induction of tonsil B cell proliferation and immunoglobulin (Ig) production, provided the combination of interleukin (IL)‐2 and IL‐10 was added to cultures. CD8+T cell clones, with intermediate levels of CD40L expression (10 to 30 CD40L+cells), also stimulated B cell proliferation and Ig secretion with IL‐2 and IL‐10. B cell responses induced by these CD8+T cell clones were neutralized by blocking monoclonal antibodies specific for either CD40L or CD40. By contrast, CD40L−−T cell clones (⩽5 CD40L+cells), only induced marginal B cell responses even with IL‐2 and IL‐10. All three clone types were able to activate B cells as shown by up‐regulation of CD25, CD80 and CD86 expression. A neutralizing anti‐CD40L antibody indicated that T cell‐dependent B cell activation was only partly dependent on CD40‐CD40L interaction. These CD40L−−clones had no inhibitory effects on B cell proliferation induced by CD40L‐expressing CD8+T cell clones. Taken together, these results indicate that CD8+T cells can induce B cell growth and differentiat