Development of graft-vs.-host disease-like syndrome in cyclosporine- treated rats after syngeneic bone marrow transplantation. I. Development of cytotoxic T lymphocytes with apparent polyclonal anti-Ia specificity, including autoreactivity

Identification of the Effector Cell Mediating Lysis. We attempted to identify the effector cell which mediated the lysis of the ACI and Lewis target cells. Fig. 3 shows the results of a representative experiment in which nylon wool-nonadherent spleen cells, from a CsA-treated syngeneic marrow transplant recipient exhibiting clinical evidence of syngeneic GVHD, were fractionated into distinct subpopulations, as recognized by mAb for rat T lymphocyte subsets. The results demonstrate that depletion of the T cell subset with the pan-T mAb W3/13 Normal Lewis rats were treated with CsA or the control diluent (15 mg/kg/d for 40 d). Spleen cells from these animals were harvested 14-21 d after withdrawal of CsA therapy, and passed over nylon wool. The nonadherent spleen cells were tested for their ability to lyse 5~Cr-labelled ACI, Lewis, or BN blast cells at an effector/target ratio of 100:1. * Mean percent specific 5~Cr release -+SE. removed the spleen ceil-mediated cytotoxic activity against ACI and Lewis target cells. The majority of the activity was recovered in the adherent fraction. In contrast, panning of the nylon wool-nonadherent spleen cells with the W3/25 (which identifies rat helper T cells) did not result in a significant decrease of activity, but rather, resulted in a slight enhancement of cytotoxic activity against ACI and Lewis target cells. Cells from the adherent fraction from this panning procedure did not mediate significant lysis of either target cell. In contrast, removal of the OX8 ÷ cells (OX8 represents the rat non-helper T cell subset) resulted in a significant reduction of cytotoxic activity against both ACI and Lewis target cells. The cytotoxic activity was recovered in the adherent fraction.