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SUMMARY: Antihuman antilymphoeyte sera inhibit, in vitro the formation of rosettes between human peripheral lymphocytes and sheep red blood cells. This inhibition is increased by the presence of complement. Eighteen horse antilymphocyte sera have been tested in vitro for leukoagglutination, lymphocytotoxicity, and rosette inhibition without information on their in vivo effect. The rosette inhibition titres, measured in the presence of complement, were always much higher than leukoagglutination and cytotoxic titres. The immunosuppressive potency of the 18 sera, which had been evaluated by measuring the prolongation of allogenic skin graft survival in macaques and chimpanzees, was well correlated with the rosette inhibition titres. Conversely, the correlation was not satisfactory for leukoagglutination and cytotoxicity titres. The simple and easily reproducible rosette inhibition test can apparently be used for evaluation of imnumosuppressive activity of antihuman sera, but. it cannot predict their toxicity.
Bach et al. (Mon,) studied this question.