title: Recovery of antitumor CD4+ T cell responsiveness, suppressed in the tumor-bearing state, by release from tumor burden.
abstract: The present study investigates the recovery of antitumor CD4+ T cell responsiveness, suppressed in the tumor-bearing state, following release of tumor burden. Spleen cells from BALB/c mice bearing a syngeneic tumor (CSA1M) 1-3 weeks after the inoculation with CSA1M cells produced interleukin-2 (IL-2) and IL-4 upon in vitro cultures without addition of exogenous tumor antigens. This lymphokine production was achieved through collaboration between anti-CSA1M CD4+ T cells and antigen-presenting cells (APC) that has been pulsed with CSA1M tumor antigens in vivo in the tumor-bearing state. The lymphokine-producing capacity gradually decreased as the tumor-bearing period increased, and spleen cells from mice at late (8-10 week) tumor-bearing stages produced reduced levels of lymphokines. Because APC in these cells exhibited enhanced capacities to present tumor antigens, the reduced responsiveness was ascribed to the dysfunction of CD4+ T cells themselves. However, removal of a tumor after 8 weeks resulted in a remarkable recovery of the lymphokine-producing capacities of whole spleen cells. In contrast to the reduction in CSA1M-antigen-presenting activity of APC following tumor resection, CD4+ T cells exhibited a reciprocal increase in their responsiveness to CSA1M antigens. The recovery of antitumor responsiveness was also observed in the in vitro cultures free from tumor burden; when spleen cells from mice at late tumor-bearing stages were pre-incubated for 1-2 days and re-cultured in fresh medium, they produced potent amounts of IL-2 and IL-4. These results indicate that the immunodysfunction of antitumor CD4+ T cells induced in the tumor-bearing state is not irreversible, and release from tumor burden results in almost complete recovery of the potent antitumor responsiveness they previously expressed.
authors.affiliation: Biomedical Research Center, Osaka University Medical School, Japan.
authors.forename: J P
authors.initials: JP
authors.lastname: Zou
authors.forename: T
authors.initials: T
authors.lastname: Nagata
authors.forename: N
authors.initials: N
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Ono
authors.forename: H
authors.initials: H
authors.lastname: Fujiwara
authors.forename: T
authors.initials: T
authors.lastname: Hamaoka
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology; D000951:Antigens, Neoplasm / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003470:Culture Media; D007108:Immune Tolerance; D007376:Interleukin-2 / Q000096:biosynthesis; D015847:Interleukin-4 / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000276:immunology* / Q000601:surgery; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000951:Antigens, Neoplasm; D003470:Culture Media; D007376:Interleukin-2; D015847:Interleukin-4