The intrinsic homeostatic mechanisms that occur during the initial antigen-induced activation of CD4⁺ T cells control the magnitude and class of immune responses, including the emergence of T_H1, T_H2, and T_H17 effectors and CD4⁺CD25⁺Foxp3⁺-, Tr1-, and CD4⁺-converted DN regulatory cells. The dichotomy of T_H1 and T_H2 T-cell subsets, the reciprocal differentiation of Treg's and T_H17 effectors, and AICD elucidate how the intrinsic homeostatic mechanisms control the magnitude and class of immune responses to infectious organisms and tissue inflammation. A new pathway of differentiating previously unidentified DN Treg's represents a negative feedback mechanism that regulates the magnitude of immune responses.