Immune responses in small intestinal transplantation in the rat: correlation of histopathology and monocyte procoagulant activity.

No predictive serologic marker exists for rejection or graft versus host disease (GVHD) reactions in small intestinal transplantation (SIT). SIT was performed in Lewis (Lew) and Lew X Brown Norway Fl hybrid (LBN) rats in the following combinations: group 1, Lew X Lew; group 2 (isolated rejection), LBN X Lew, and group 3 (isolated GVHD), Lew X LBN. Procoagulant activity (PCA), an index of monocyte immune activation, was measured in the peripheral blood mononuclear cells of graft recipients to assess its value as an immunologic monitor. Histologic findings and PCA were evaluated on days 1, 2, and 3 and every 2 to 3 days after SIT. No pathologic findings of graft or host tissue developed in group 1 (n = 14). Histologic rejection (blunted villi and mononuclear cell infiltration) was seen beginning on day 5 in group 2 (n = 19); early GVHD (loss of nodal and splenic architecture) was first noted on days 5 and 6 in group 3 (n = 17). PCA elevation in SIT was seen to precede histologic evidence of rejection or graft versus host disease in this model and may constitute an important marker for these immunologic events.