High‐ and low‐leukemogenic variants of the radiation leukemia virus (RadLV) differ in ability to induce tumor‐specific immune suppression

Abstract

Adult C57BL/6 mice inoculated intrathymically (i.t.) with the highly leukemogenic variant of the radiation leukemia virus (A-RadLV) develop suppressor cells capable of specifically abrogating a potential anti-tumor cytotoxic response in vitro. Suppressor cells were generated directly by the virus, independently of an initiation of a leukemogenic process. Inoculation of C57BL/6 animals with the low leukemogenic D-RadLV variant did not result in suppressor cell generation. It is proposed that induction of tumor-specific immune suppression by A-RadLV is essential for tumor progression, and the leukemogenic activity of D-RadLV is attributed to its inability to recruit suppressor cells.

Potentiation of T cell immunity against radiation-leukemia-virus-induced lymphoma by polysaccharide K

“…In Fig. 2, as well as in previous work [16,18,19], we demonstrated that R/B6 splenocytes contain Ts cells that suppress the anti-YAß3-proliferative responses. Addition of R/B6 cells to the stimulation culture also suppressed the generation of anti-YAB3 Tc lymphocytes (Fig.…”

“…The experimental system chosen for these studies was RadLV-induced leukemogenesis in Bö mice because (a) this virus induces a long premalignant state in the mouse, characterized by the appearance ofpreleukemic cells [6,7]; (b) RadLV-infected cells are potentially immunogenic ow-60 ing to expression of virus structural proteins in the cells [18][19][20], and (c) virus-specific Ts lymphocytes that emerge early in the preleukemic latency arbrogate the elicitation of anti-RadLV immune responses, which otherwise would interfere in the progression of the premalignant evolution process [16,18,19,21].…”

“…For several years, our laboratory has been engaged in studies on the immunobiology of lymphomas induced by the Radiation Leukemia Virus (RadLV) [1,2,[16][17][18][19][20][21][22]. RadLV is a slow-acting retrovirus, which induces thymic lymphomas in C57BL mice after a latent period of 3 -6 months [10].…”

Suppressor and reactive lymphocytes in radiation leukemia virus (RadLV)-induced leukemogenesis

“…Previous work in our laboratory demonstrated that suppressor T lymphocytes appeared in the spleen of B6 mice shortly after they had been inoculated with the highly leukemogenic A-RadLV [21]. These suppressor cells could inhibit proliferative and cytotoxic responses in B6 lymphocytes towards the syngeneic A-RadLV-induced T-cell leukemia 136.5, and were not detected in mice inoculated with the low-leukemogenic D-RadLV variant [20]. We therefore suggested that the high leukemogenic activity of A-RadLV is associated with the virus' ability to recruit suppressor cells in the host which sustain the leukemogenic process by protecting preleukemic cells from immune destruction.…”

“…Inoculation of D-RadLV does not result in suppressor cell generation [20]. It was therefore postulated that suppressor cells generated early in leukemogenesis interfere with a potential anti-tumor immunity which would otherwise arrest tumor progression.…”