Activation or destruction of T cells via macrophages.

Macrophages (MPhi) affect the T cell response in two mutually exclusive ways: activation or deletion. A MPhi type with T cell activating functions (M1) is able to express and upregulate receptors of the B7 family. IFN-gamma favours this MPhi differentiation pathway via upregulation of CD80 (B7-1) and CD86 (B7-2). The treatment of MPhi with IFN-gamma enhances the alphaCD3-mediated T cell blast transformation and reduces the fraction of deleted T cells. This MPhi type may prevent antibody-mediated T cell destruction by the expression of costimulatory receptors. An IL-10-induced MPhi type (M2) fails to express costimulatory molecules of the B7 family but is an effective cell for T cell destruction. Forming cellular conjugates with T cells through antibodies or immune complexes, M2-MPhi preferentially delete targeted cells in vitro and in vivo. Copyright 2000 S. Karger AG, Basel.