Abstract Intracellular/autocrine complement proteins have emerged as critical regulators of human Th1 induction and contraction. T cells contain both intracellular C3 C5 activation systems, with C3aR1 C5aR1 stimulation driving cell homeostatic survival normal IFNg production, respectively. Here we demonstrate how the intracellular/autocrine system is regulated by using from first described pati...