Relation of suppressor activity to lymphocyte subsets, in vitro IL‐2R expression, and biopsy results in cardiac transplant patients

Nonspecific suppressor activity of peripheral blood mononuclear cells (PBMC) was determined from 8 patients preoperatively and 22 patients subsequent to heart transplantation. Whereas no correlation was found between any defined lymphocyte subsets, in vitro interleukin‐2 (IL‐2) production, and IL‐2R expression, or biopsy‐proven rejection and suppressor cell activity when data obtained on the same day as the suppressor assay were analysed, the phytohemagglutinin — but not the concanavalin A induced, in vitro IL‐2 production — was significantly enhanced (P < 0.02) in patients with evidence of concomitant rejection. In contrast, a significant correlation between diminished, nonspecific suppression and rejection was found when the results of biopsies performed up to 2 (P < 0.0075) and 4 (P < 0.0033) weeks after the investigation of suppressor cell activity were compared. We conclude that periodic determination of the suppressor functional status may be useful to discriminate between patients at low or high risk for graft rejection after heart transplantation.