title: Changes in spleen cell proliferative responses and resistance to syngeneic tumor challenge in aging NBR rats.
abstract: New Zealand Black rats are shown to have a mean longevity of 102.9 weeks. The 90%, 50% and 10% survival age are 81 weeks, 108 weeks and 126 weeks, respectively. Resistance to syngeneic tumor challenge is significantly lower in young rats (3-35 weeks) and very old rats (126-140 weeks) compared to middle-aged rats (36-85 weeks). The in vitro spleen cell proliferative response to syngeneic tumor cells is decreased in old rats. No decrease is observed in spleen cell proliferation induced by the mitogens concanavalin A or phytohemagglutinin. Young (4 weeks) rat spleens contain suppressor cells which affect the mitogen and syngeneic tumor cell induced proliferation of responsive spleen cells (from 50-week-old rats). Spleen cells from old rats (130 weeks) do not demonstrate analogous suppressor cell activity.
mesh_terms: D000375:Aging; D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005354:Fibrosarcoma / Q000276:immunology* / Q000473:pathology; D007111:Immunity, Cellular; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D008934:Mitogens / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013154:Spleen / Q000166:cytology / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D008934:Mitogens