| Abstract: | Tolerance to sheep's red blood cells (SRBC) was induced in (CBA×C57BL/6)F1 mice by a single intraperitoneal injection of 6×109 SRBC followed by injection of 100–200 mg/kg cyclophosphamide 44–46 h later. Spleen cells of tolerant mice, obtained at various times (12–26 days) after induction of tolerance, when injected into intact syngeneic recipients, did not depress their immune response to SRBC. Unlike intact mice, tolerant mice were unable to produce suppressor cells after a single immunization with SRBC. Only if three additional injections of large doses (6×109) of SRBC were given to the tolerant mice did their spleen cells acquire the ability to inhibit the immune response on injection into normal mice. It is postulated that the absence of suppressor cells on induction of immunologic tolerance by means of cyclophosphamide is due to clonal elimination. Suppressor cells may arise in tolerant animals under the influence of intensive antigenic stimulation, leading to deepening of the state of tolerance as a result of additional injections of SRBC.Laboratory of Immunogenetics, Institute of Medical Genetics, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Zhukov-Verezhnikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 86, No. 11, pp. 558–560, November, 1978. |
