Minimal costimulatory requirements for T cell priming and TH1 differentiation: activation of naive human T lymphocytes by tumor cells armed with bifunctional antibody constructs.
Direct priming of naive human CD8+ and CD4+ T cells by tumor cells devoid of any intrinsic antigen presentation properties, but passively armed with recombinant proteins mediating primary and costimulatory T cell signals, was investigated. Bifunctional antibody constructs were used to specifically target costimulatory molecules such as B7-1, B7-2 and LFA-3 to the epithelial cell adhesion molecule (EpCAM), a surface antigen successfully used as target for antibody therapy of minimal residual colorectal cancer. T cell priming was monitored by flow cytometric analysis of CD45 isoform expression and confirmed by measuring typical effector functions of primed T cells known to be absent from naive T lymphocytes. Accordingly, CD8+ T cells were tested for cytotoxic activity and secretion of TNF-alpha, while secretion of IFN-gamma, IL-5 and IL-4 was determined for CD4+ T cells. B7, known to be required for the initial activation of naive T cells, also proved to be sufficient for T cell priming when present as the only costimulatory molecule together with an appropriate primary signal. The requirement of dendritic and other antigen presenting cells (APCs) for T cell priming through non-APCs such as tumor cells could be ruled out. Under minimal priming conditions, naive CD4+ T cells were found to exclusively enter the TH1 developmental pathway, while several factors thought to favor TH2 polarization, like weak primary signals and B7-2 versus B7-1 costimulation, could be excluded as dominant TH2 promoters.
Institute of Immunology, Goethestrasse 31, 80336 Munich, Germany. Kufer@ifi.med.uni-muenchen.de
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P
Kufer
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Zettl
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K
Borschert
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Lutterbüse
R
R
Kischel
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Riethmüller
D000818:Animals; D018033:Antibodies, Bispecific / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D017951:Antigen Presentation; D015703:Antigens, CD / Q000235:genetics; D000951:Antigens, Neoplasm / Q000276:immunology*; D018122:B7-1 Antigen / Q000235:genetics; D051940:B7-2 Antigen; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018968:CD58 Antigens / Q000235:genetics; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D016466:CHO Cells; D015815:Cell Adhesion Molecules / Q000276:immunology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D006224:Cricetinae; D016207:Cytokines / Q000096:biosynthesis; D000071858:Epithelial Cell Adhesion Molecule; D006801:Humans; D017493:Leukocyte Common Antigens / Q000378:metabolism; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000235:genetics; D009369:Neoplasms / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology
D018033:Antibodies, Bispecific; D015703:Antigens, CD; D000951:Antigens, Neoplasm; D018122:B7-1 Antigen; D051940:B7-2 Antigen; D018968:CD58 Antigens; C497964:CD86 protein, human; D015815:Cell Adhesion Molecules; D016207:Cytokines; D000071858:Epithelial Cell Adhesion Molecule; D008562:Membrane Glycoproteins; D011994:Recombinant Proteins; D017493:Leukocyte Common Antigens