Effect of immunosuppressive therapy for renal allografts on the number of circulating sheep red blood cells rosetting cells.

Patients receiving renal allografts from relatively incompatible donors were randomly assigned to one of two immunosuppressive regimens: azathioprine and prednisone with or without a 2-week course of horse antihuman thymocyte globulin (ATG). The number of circulating lymphocytes fell to about one-third of pretreatment values in both groups of patients. In patients given ATG, the proportion of sheep red blood cell-rosetting lymphocytes (SRBC-R) fell promptly to less than 10% of pretreatment values. In contrast, the percentage of SRBC-R remained at about 70% in patients receiving only prednisone and azathioprine. The addition of ATG reduced the number of SRBC-R/mm3 to one-tenth to one-thirtieth the number seen in non-ATG-treated patients. Plasma of patients undergoing therapy did not inhibit rosetting in vitro. It is proposed that the monitoring of circulating rosetting cells may be a useful clinical guide to the degree of T cell immunosuppression. It is also suggested that the regimen of azathioprine, prednisone, and ATG results in a more effective suppression of circulating T cells than that produced by azathioprine and prednisone alone.