antilymphocyte serum

(immunology) An immunosuppressive agent effective in prolonging the lives of homografts in experimental animals by reducing the circulating lymphocytes.

(Abbr. ALS) The globulin fraction of serum from a horse or another animal, usually used in conjunction with other immunosuppressive agents to suppress rejection of grafts or organ transplants.

Antiserum containing antibodies specific for lymphocyte surface antigens that may be used to suppress delayed type hypersensitivity, particularly graft rejection, responses without affecting humoral immune response; abbreviated ALS. Used in organ transplantation, usually in combination with immunosuppressive drugs. Prepared by hyperimmunizing an animal, e.g. horse, with foreign, e.g. human, lymphocytes. See also antilymphocyte globulin.