Importantly, CD46‐mediated signals were specifically required for normal Th1, but not Th2 responses, because the IL‐4 and IL‐5 levels were unaltered in SLE T cells after CD3+CD46 activation (Fig. 1D) or after CD3 and CD3+CD28 stimulation (not shown). This evidence concerns the gene CD28 and systemic lupus erythematosus.