Immunotherapy of the Dunning leukaemia with thymic extracts.

Injections of thymic extract (TE), TE primed lymphocytes or normal lymph node cells were effective in bringing about total remission of the Dunning leukaemia in inbred Fisher CD rats. Survival greater than 365 days occurred in 10-80% of the various treated groups whereas untreated leukaemic rats, or leukaemic rats treated with spleen "mock thymus extract" or bovine serum albumin, died within an average of 10-17 days. Administration of antilymphocyte serum into leukaemic rats enhanced their death rate. Stimulation of cell mediated immunity via the production of functional thymus stimulated lymphocytes is postulated as the mechanism by which tumour rejection occurred.