Stress induced shedding of a tumor antigen by a rat histiocytic cell line AK-5: a possible mechanism of immune evasion.
AK-5 is a highly immunogenic tumor which stimulates multiple arms of the host immune system. Tumor cells when transplanted subcutaneously grow as solid tumors which are regressed in about 70% of animals, whereas 100% i.p. transplanted animals succumb to the tumor growth. In the present study we demonstrate shedding of an antigen by AK-5 cells when subjected to stress such as low cell number transplantation in vivo, heat shock and serum starvation in vitro. The shed antigen is able to neutralize antitumor antibody in a complement fixation assay. The antigen is also detected in the cell-free ascitic fluid. The size of the shed antigen as recognized by anti-AK-5 antibody is approximately 45 kDa. We have also studied some of the biochemical characteristics of the purified shed antigen. These observations suggest a positive role for the AK-5 antigen in immune recognition which is lost in i.p. transplanted tumor cells due to the shedding of the antigen, thereby escaping the immune invasion.
Centre for Cellular and Molecular Biology, Hyderabad, India.
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Gopalkrishna
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Begum
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Khar
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification / Q000378:metabolism*; D015153:Blotting, Western; D003168:Complement Fixation Tests; D016895:Culture Media, Serum-Free; D018219:Histiocytoma, Benign Fibrous / Q000276:immunology* / Q000473:pathology; D006358:Hot Temperature; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009368:Neoplasm Transplantation; D051381:Rats; D017208:Rats, Wistar; D012878:Skin Neoplasms / Q000276:immunology / Q000473:pathology; D013312:Stress, Physiological; D013997:Time Factors; D014407:Tumor Cells, Cultured
D000596:Amino Acids; D000951:Antigens, Neoplasm; D016895:Culture Media, Serum-Free