Characterization of Antilymphocytic Antibody

Abstract

ANTILYMPHOCYTIC serum (ALS) is now well known to have the power of prolonging the life of homografts on the animals into which it is injected^1–3. All who have studied ALS agree that a high proportion of its immunosuppressive power resides in the 7S globulin fraction². The experiments described here represent a formal analysis of the power of different fractions of ALS raised in rabbits and horses to prolong the life of A-strain tail skin homo-grafts on CBA mice. Rabbit antisera against mouse thymocytes were prepared by the method of Levey and Medawar³. The horse antiserum, made by a scaled-up variant of the same technique, was kindly supplied to us by the Wellcome Foundation. The serum fractions were normally reconstituted to the concentrations at which they were originally present in whole serum, and assayed by the subcutaneous injection of 0.5 ml. on the second and again on the fifth days after skin grafting³.