Suppression of the local graft-vs.-host reaction in rats by treatment with a monoclonal antibody specific for the interleukin 2 receptor.

Local graft-vs.-host reaction (GVHR) was induced in rats by injecting parental cells into young F1 recipients. As a consequence of antigenic stimulation in the course of developing GVHR in the responding lymph nodes, the number of interleukin 2-receptor (IL 2R)-bearing T cells increased from less than 1% up to 10% of the total population. The IL 2R-bearing cells were located mainly in the T cell areas of the reactive lymph nodes. As assessed by the determination of the GVHR indices, treatment of the recipients with anti-T-helper subset-specific mAb (W3/25) or with anti-IL 2R mAb (ART-18) inhibited the GVHR. In parallel, the number of IL 2R-bearing cells was reduced to the normal levels. W3/25 mAb treatment changed the helper/suppressor subset ratio and reduced the number of circulating lymphocytes in the peripheral blood. In contrast, ART-18 mAb treatment did not induce any detectable changes in the subset distribution and it did not affect the number of circulating lymphocytes. The results demonstrate the key role that the IL 2R-positive cells play in the proliferative phase of acute GVHR, and favor the use of anti-IL 2R mAb as selective immunosuppressive agents.