Studies on the rosette inhibition assay. Improvement of the method and correlation with monkey skin graft prolongation.

The rosette inhibition assay for immunosuppressive activity of antilymphocyte globulin or plasma has been studied in an effort to improve its reliability. Important changes include the elimination of calcium and magnesium ions from salt solutions used in the assay, the use of deoxyribonuclease to prevent lymphocyte clumping, and pretreatment of plasma samples (heating at 63 C for 10 min followed by acrinol precipitation) to prevent nonspecific inhibition of rosette formation. The use of a graded dose response potency assay against a house standard is discussed. A significant correlation was established between the in vitro activity of several series of antilymphocyte globulin or antithymocyte globulin preparations and their ability to prolong skin graft survival in primates. The best correlation was achieved using a potency estimate relative to a house standard, rather than the conventional titer estimate.