title: Specific MDR1 P-glycoprotein blockade inhibits human alloimmune T cell activation in vitro.
abstract: MDR1 P-glycoprotein (P-gp), the multidrug resistance-associated transmembrane transporter, is physiologically expressed by human peripheral immune cells, but its role in cell-mediated immunity remains poorly understood. Here, we demonstrate a novel role for P-gp in alloantigen-dependent human T cell activation. The pharmacologic P-gp inhibitor tamoxifen (1-10 microM) and the MDR1 P-gp-specific mAb Hyb-241 (1-20 microg/ml), which detected surface P-gp on 21% of human CD3(+) T cells and 84% of CD14(+) APCs in our studies, inhibited alloantigen-dependent, but not mitogen-dependent, T cell proliferation in a dose-dependent manner from 40-90% (p < 0.01). The specific inhibitory effect on alloimmune T cell activation was associated with >85% inhibition (p < 0.01) of IL-2, IFN-gamma, and TNF-alpha production in 48-h MLR coculture supernatants. Addition of recombinant human IL-2 (0.1-10 ng/ml) restored proliferation in tamoxifen-treated cocultures. Pretreatment of purified CD4(+) T cells with Hyb-241 mAb before coculture resulted in inhibition of CD4(+) T cellular IFN-gamma secretion. Also, blockade of P-gp on allogeneic APCs inhibited IL-12 secretion. Taken together these results demonstrate that P-gp is functional on both CD4(+) T cells and CD14(+) APCs, and that P-gp blockade may attenuate both IFN-gamma and IL-12 through a positive feedback loop. Our results define a novel role for P-gp in alloimmunity and thus raise the intriguing possibility that P-gp may represent a novel therapeutic target in allograft rejection.
authors.affiliation: Division of Nephrology, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: M H
authors.initials: MH
authors.lastname: Frank
authors.forename: M D
authors.initials: MD
authors.lastname: Denton
authors.forename: S I
authors.initials: SI
authors.lastname: Alexander
authors.forename: S J
authors.initials: SJ
authors.lastname: Khoury
authors.forename: M H
authors.initials: MH
authors.lastname: Sayegh
authors.forename: D M
authors.initials: DM
authors.lastname: Briscoe
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000502:physiology*; D000276:Adjuvants, Immunologic / Q000037:antagonists & inhibitors / Q000502:physiology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D018664:Interleukin-12 / Q000378:metabolism; D007519:Isoantigens / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D007166:Immunosuppressive Agents; D007519:Isoantigens; D013629:Tamoxifen; D018664:Interleukin-12