Figure 4.

Blockade of effector T cells allowing the in vivo expansion of alloreactive/self-reactive T_R cells: a putative immunotherapy for transplantation or autoimmunity. Following transplantation both harmful effector T cells (T_E) and suppressive natural regulatory cells (T_R) are recruited to the graft. In the normal physiological state, there are too few T_R cells or their function is too weak to beneficially suppress the large precursor frequency of graft destructive T_E cells (a). Administration of an immunotherapeutic agent (e.g. non-depleting anti-CD4) specifically blocks T_E cells but allows the function and, more importantly, alloreactive expansion of T_R cells (b). The large expanded population of T_R cells then renders the graft operationally tolerant (c). Essentially similar principles can be applied in the case of autoimmunity.