“…There are numerous studies in the literature of the preventive effect of 6-mercaptopurine (6-MP) in the primary and secondary immune responses in skin and renal homografts, protein antigens, experimental allergic encephalomyelitis, and intramyocardial injections of streptococci (Schwartz, Stack, and Dameshek, 1958;Meeker, Condie, Weiner, Varco, and Good, 1959;Schwartz andDameshek, 1959, 1960;Schwartz, Eisner, and Dameshek, 1959;Calne, 1960;Hoyer, Condie, and Good, 1960;Thomas, Morton, Crane, and Gardner, 1961;Zukoski, Lee, and Hume, 1961;Pierce and Varco, 1962;Laufer, Ginsburg, Gery, and Davies, 1963).…”