Innate and adaptive immune responses to nonvascular xenografts: Evidence that macrophages are direct effectors of xenograft rejection

Abstract

Nonvascularized xenograft rejection is T cell mediated, but is dependent on initial macrophage (Mφ) infiltration. We developed an i.p. transplant model to define the roles of Mφ and T cells in xenograft rejection. Nonobese diabetic or BALB/c mice were injected i.p. with xenogeneic, allogeneic, or syngeneic cells, and the responding cells in subsequent lavages were assessed by flow cytometry and adoptive transfer. Neutrophils and monocytes/elicited Mφ were rapidly recruited in response to xenogeneic pig (PK15 or spleen) cells and, to a significantly lesser extent, allogeneic cells. These innate responses preceded T cell infiltration and occurred in their absence in SCID mice. Syngeneic cells ..