Chronic antagonism of Mig inhibits cellular infiltration and promotes survival of class II MHC disparate skin allografts.

Background. The goal of the current study was to test the ability of monokine induced by IFN-gamma (Mig)-specific antibodies to inhibit long-term T cell infiltration into class II major histocompatibility complex (MHC) disparate skin allografts and to test cellular and molecular changes in the graft during the rejection observed following cessation of treatment. Methods. C57BL/6 recipients of B6.H-2(bm12) skin grafts were treated with normal rabbit serum (NRS) or rabbit Mig antiserum. (Mig AS) every other day from day 7 until day 21 posttransplant and then weekly thereafter. Allografts were retrieved during the course of treatment and following cessation. Tissue sections were prepared and stained to compare infiltration by macrophages and CD4(+) and CD8(+) T cells and to assess collagen deposition in the grafts. RNA was prepared and tested by ribonuclease protection assay for intragraft levels of Mig, monocyte chemotactic protein-1 (MCP-1) and regulated on activation normal T-cell expressed and secreted (RANTES). Results. T cell and macrophage infiltration into allografts was inhibited and graft survival. maintained as long as Mig-specific antibodies were given. Following cessation of treatment, T cells and macrophages infiltrated the allografts. In contrast to the histology of acute rejection observed in allografts from NRS-treated recipients, the resulting rejection of the allografts from Mig AS-treated recipients was accompanied by dense collagen deposition and high level expression of Mig and RANTES. Conclusions. Mig directs T cell infiltration into B6.H-2(bm12) skin allografts on C57BL/6 recipients. Delayed T cell and macrophage infiltration and rejection of the grafts following cessation of Mig AS treatment results in rejection that is histologically and molecularly distinct from acute rejection.