[Enhancement of T cell-mediated immune responses in KMT-17-bearing rats by treatment with bleomycin].
The strong antitumor resistance was induced after the complete cure of a KMT-17 fibrosarcoma in WKA rats treated with bleomycin (BLM, 5 mg/kg/day, ip, for 5 days from Day 8). This suggests that immune responses of the hosts may participate in the therapeutic effects of BLM. The immune responses against the tumor associated antigens (TAA) of KMT-17 tumor cells were examined by assaying the cytotoxic T lymphocyte (CTL) activity of spleen cells after a mixed lymphocyte tumor culture (MLTC). The non-treated tumor-bearing rats showed slight responses on Day 5 and the responses reached the peak on Day 8. On Day 11, however, the responses could not be detected further. On the other hand, the responses were restored and augmented in the BLM-treated rats. The responses could be detected on the next day after the end of BLM treatment (Day 13) and were able to maintain for at least one month. Furthermore, the augmentation of T cell-mediated responses against TAA in BLM-treated rats was found to be due to the elimination of suppressor T cell activity appearing in the course of tumor progression. The T cell-fraction of spleen cells obtained from non-treated tumor-bearing rats inhibited the responses of hyperimmune rats, while the fraction obtained from BLM-treated tumor-bearing and normal rats did not. The antigen presenting cell (APC) activity of macrophages involved in T cell responses was not altered significantly by the tumor growth or BLM treatment. Moreover, macrophages of non-treated tumor-bearing rats did not show any suppressor activity on the T cell responses. The antitumor activity of CTL generating after the MLTC was detected not only by the in vitro 51Cr release assay but also by the in vivo tumor neutralizing assay (Winn's assay).
D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology; D001761:Bleomycin / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D005354:Fibrosarcoma / Q000188:drug therapy / Q000276:immunology*; D007111:Immunity, Cellular / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
D000951:Antigens, Neoplasm; D001761:Bleomycin