Production of soluble HLA-class-I molecules by IFN-gamma-induced colon-adenocarcinoma cells.
High levels of soluble HLA-class-I molecules (sHLA) were found to be produced in a time- and dose-dependent manner by colon-adenocarcinoma Colo205 cells in response to IFN-gamma stimulation. Among other cytokines tested, only IL-6, TNF, IFN-alpha and IFN-beta showed weak inducibility. IFN-gamma-induced production of sHLA was synergistically enhanced by IL-1 alpha, IL-6 or TNF, and combined treatment with TNF and IL-6 exhibited an additive to synergistic induction. Expression of sHLA is unlikely to result from IFN-gamma-induced enhancement of overall HLA-class-I expression, as at low concentrations IFN-alpha, IFN-beta and IFN-gamma stimulated increased expression of cell membrane HLA-class-I molecules in Colo205 cells with almost equal efficiency, whereas only IFN-gamma induced high level production of sHLA. Immunoblotting with a monoclonal antibody recognizing beta 2-microglobulin-free HLA-class-I heavy chain revealed 3 major forms of sHLA heavy chain, i.e., 45/43-, 37- and 33-kDa molecules, in the culture supernatants of IFN-gamma-induced Colo205 cells. The 45/43-kDa proteins can be partitioned into Triton X-114, representing intact HLA-class-I heavy chains shed from the cell membrane. The hydrophilic 37- and 33-kDa heavy chain, which remained almost exclusively in the aqueous phase after extraction with Triton X-114, could well be due to alternative RNA splicing, with deletion of exon 5 encoding the hydrophobic transmembrane region of membrane-anchored HLA-class-I heavy chain.
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J
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Department of Microbiology, New York University Medical Center, New York 10016.
Hua
J C
JC
D000230:Adenocarcinoma / Q000276:immunology* / Q000378:metabolism; D000911:Antibodies, Monoclonal; D003110:Colonic Neoplasms / Q000276:immunology* / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D015972:Gene Expression Regulation, Neoplastic; D005805:Genes, MHC Class I; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000737:chemistry; D006801:Humans; D015151:Immunoblotting; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry; D007371:Interferon-gamma / Q000494:pharmacology*; D008970:Molecular Weight; D017830:Octoxynol; D011092:Polyethylene Glycols; D011994:Recombinant Proteins / Q000494:pharmacology; D012995:Solubility; D013268:Stimulation, Chemical; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
D000911:Antibodies, Monoclonal; D016207:Cytokines; D015395:Histocompatibility Antigens Class I; D007143:Immunoglobulin Heavy Chains; D011994:Recombinant Proteins; D011092:Polyethylene Glycols; D007371:Interferon-gamma; D017830:Octoxynol; C010615:Nonidet P-40