title: Evidence for a functional receptor for cyclosporin A on the surface of lymphocytes.
abstract: Cyclosporin A (CsA) is an immunosuppressive agent that inhibits the synthesis of lymphokines by T lymphocytes at the level of transcription. A cytoplasmic protein, cyclophilin, is the most thoroughly studied CsA-binding protein, but its ubiquitous presence in cells of all types raises questions about its role in immunosuppression. In an attempt to ascertain the presence of a cell surface receptor, we synthesized two polyvalent macromolecular CsA derivatives, CsA-BBa-ovalbumin and CsA-BBa-aminodextran (CBD), from the product of the photochemical reaction of CsA and 4-benzoylbenzoic acid (CsA-BBa). (i) They inhibited the peptidylprolyl cis-trans isomerase activity of cyclophilin and the synthesis of interleukin 2 by phorbol ester-activated EL-4 cells. (ii) CBD also inhibited interleukin 2 secretion by Con A-activated T-cell-enriched mouse splenocytes. 4-Benzoylbenzoic acid (BBa)-aminodextran and aminodextran were inactive. (iii) Direct binding and competition studies with [3H]CsA indicated that CBD does not enter EL-4 cells (i.e., it acted at the surface). (iv) CBD caused agglutination of EL-4 cells, murine B and T lymphocytes, human thymocytes, and two T-cell hybridomas. Agglutination was inhibited by a monoclonal antibody to CsA and by CsA and CsA-BBa, but not by BBa. No agglutination was seen with BBa-aminodextran or aminodextran. HeLa cells, Vero (monkey kidney) cells, a mouse plasmacytoma, COS cells, and a poorly differentiated B-cell lymphoma were not agglutinated. (v) EL-4 cells failed to be agglutinated after treatment with trypsin or chymotrypsin. Specific agglutination was again possible after incubation for 5 h at 37 degrees C in the absence of enzyme. (vi) CBD covalently linked to crosslinked agarose beads inhibited interleukin 2 production by phorbol ester-stimulated EL-4 cells. No activity was seen if cell-to-bead contact was prevented by a 0.02-microns microporous filter that did not interfere with the passage of CBD. Our findings support the presence of a functional receptor on the surface of selected cells of the immune system.
authors.affiliation: Department of Microbiology, Columbia University, New York, NY 10032.
authors.forename: N A
authors.initials: NA
authors.lastname: Cacalano
authors.forename: B X
authors.initials: BX
authors.lastname: Chen
authors.forename: W L
authors.initials: WL
authors.lastname: Cleveland
authors.forename: B F
authors.initials: BF
authors.lastname: Erlanger
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D016572:Cyclosporine / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007165:Immunosuppression Therapy; D007376:Interleukin-2 / Q000378:metabolism; D007700:Kinetics; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D011971:Receptors, Immunologic / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D007376:Interleukin-2; D011971:Receptors, Immunologic; C028752:cyclosporin receptor; D016572:Cyclosporine; D013755:Tetradecanoylphorbol Acetate