LEUKOCYTE SUBSETS IN FIRST-SET RAT CARDIAC ALLOGRAFT REJECTION

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Abstract
For an immunohistochemical analysis of the cells infiltrating rat cardiac allografts undergoing unmodified first-set rejection, functioning Wistar Furth (RT1u) cardiac allografts transplanted to Lewis (RT11) recipients were arbitrarily removed at days 3-6 posttransplantation, and were evaluated histologically using a series of monoclonal antibodies (MAbs) of known cellular distribution, the binding of which was visualized by an indirect immunoperoxidase technique. Sequestered cells present in cryostat sections were segregated numerically on the basis of staining for MAbs detecting T cells, some NK cells, and neutrophils (W3/13); cytotoxic suppressor T cells and most NK cells (MRC OX8); helper T cells and all macrophages (W3/25); B cells and a macrophage subpopulation (MRC OX6, Ia common part determinant); immature T and B cells (MRC OX7, Thy 1.1); and all leukocytes (MRC OX1, LCA). The proportion of cells stained for each MAb was expressed as a percentage of all estimated leukocytes as determined directly on the hematoxylin counterstained sections. Macrophages expressing the W3/25 and MRC OX6 antigens were enumerated on the basis of intracytoplasmic accumulation of previously administered colloidal carbon. There was a significant fall in the relative proportion of W3/25+ carbon− cells within allografts as a function of time. The proportion of mononuclear cells staining for W3/13 and for MRC OX8 showed no statistically significant variation during the period of study. There was a correlation at all periods between the proportional sum of W3/25+ carbon− cells and MRC OX8+ cells and the proportion of W3/13+ mononuclear cells present. The W3/25+ carbon−:MRC OX8+ ratio showed a significant linear decrease with duration of allograft placement. The proportion of carbon+ cells expressing the MRC OX6 and the W3/25 antigens showed a highly significant rise as a function of time. Nonspecific esterase-stained cells showed a similar sequential pattern. These data provide well defined immunohistologic parameters of leukocyte subsets present in unmodified first-set cardiac allograft rejection in the rat.