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.
Gopalkrishna
P
P
Centre for Cellular and Molecular Biology, Hyderabad, India.
Begum
Z
Z
Khar
A
A
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