Phorbol-12-myristate-13-acetate-treated human keratinocytes express B7-like molecules that serve a costimulatory role in T-cell activation.
In previous studies, Phorbol-12-myristate-13-acetate (PMA)-treated human keratinocytes (PMA-HNK) were shown to induce T-cell proliferation via a major histocompatibility complex (MHC)- and antigen (Ag)-independent mechanism, that was mediated in part by PMA-induced intercellular adhesion molecule (ICAM)-1 on HNK. Recently, the interaction of the B7 Ag on antigen-presenting cells with its ligand CD28 on T cells has been shown to deliver activation signals distinct from the interaction of MHC/Ag with the T-cell receptor. These findings led us to assess whether B7-dependent signals play a role in T-cell proliferation induced by PMA-HNK. We first examined B7 expression on HNK by staining with three different monoclonal antibodies (MoAbs). When analyzed by fluorescence-activated cell sorter, untreated HNK stained only faintly. By contrast, PMA induced a dose-dependent upregulation of B7 staining. This staining identifies a molecule closely related to B7 because it was blocked by purified recombinant B7 immunoglobulin. Upregulation of B7 staining was first observed 16 h after PMA treatment and persisted for at least 48 h; it was protein kinase C dependent and required de novo protein synthesis. Anti-B7 MoAbs reduced specifically the capacity of PMA-HNK to trigger proliferation of allogeneic peripheral blood mononuclear cells and T cells. The combination of anti-B7 and anti-ICAM-1 MoAbs further reduced this response. We conclude that PMA upregulates on HNK the expression of a B7-like molecule that contributes in concert with ICAM-1 to the capacity of PMA-HNK to induce proliferation of allogeneic T cells.
Augustin
M
M
Department of Dermatology, University of Freiburg, Germany.
Dietrich
A
A
Niedner
R
R
Kapp
A
A
Schöpf
E
E
Ledbetter
J A
JA
Brady
W
W
Linsley
P S
PS
Simon
J C
JC
D000818:Animals; D000954:Antigens, Surface / Q000032:analysis* / Q000502:physiology*; D018122:B7-1 Antigen; D015815:Cell Adhesion Molecules / Q000502:physiology; D002469:Cell Separation; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D007158:Immunologic Techniques; D018799:Intercellular Adhesion Molecule-1; D015603:Keratinocytes / Q000187:drug effects* / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D013194:Staining and Labeling; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D000954:Antigens, Surface; D018122:B7-1 Antigen; D015815:Cell Adhesion Molecules; D018799:Intercellular Adhesion Molecule-1; D013755:Tetradecanoylphorbol Acetate