Heterologous anti-lymphocyte serum and plasma.

Heterologous anti-lymphocyte serum (ALS) and plasma (ALP) are potent immuno-suppressive agents. The findings recorded in this thesis relate to their use and mode of action in thymectomized, sham-thymectomized and non-thymectomized rats and mice. No method is at present available for the in vitro standardization of ALP in terms of immuno-suppressive potency. Potency cannot be related to either, agglutinating and cytotoxic antibody titres directed against lymphocytes or to the ability of ALP to depress lymphocyte counts. The latter property of ALP has been found to be largely dependent on normal adrenal function in the recipient. The ability of ALS to prolong allograft survival times can be significantly improved if the recipient is thymectomized prior to the administration of serum and grafting performed after the completion of the course of ALS. An additional finding is that rats thymectomized in adult life show a progressive decline in immunological competence with the passage of time