Intercellular adhesion molecule-2, a second counter-receptor for CD11a/CD18 (leukocyte function-associated antigen-1), provides a costimulatory signal for T-cell receptor-initiated activation of human T cells.
Activation of T cells often requires both activation signals delivered by ligation of the TCR and those resulting from costimulatory interactions between certain T cell surface accessory molecules and their respective counter-receptors on APC. CD11a/CD18 complex on T cells modulate the activation of T cells by interacting with its counter-receptors intracellular adhesion molecule (ICAM-1) (CD54) and/or ICAM-2 on the surface of APC. The costimulatory ability of ICAM-1 has been demonstrated. Using a soluble ICAM-2 Ig fusion protein (receptor globulin, Rg) we demonstrate the costimulatory effect of ICAM-2 during the activation of CD4+ T cells. When coimmobilized with anti-TCR-1 mAb ICAM-2 Rg induced vigorous proliferative response of CD4+ T cells. This costimulatory effect of ICAM-2 was dependent on its coimmobilization with mAb directed at the CD3/TCR complex but not those directed at CD2 or CD28. Both resting as well as Ag-primed CD4+ T cells responded to the costimulatory effects of ICAM-2. The addition of mAb directed at the CD11a or CD18 molecules almost completely inhibited the responses to ICAM-2 Rg. These results are consistent with the role of CD11a/CD18 complex as a receptor for ICAM-2 mediating its costimulatory effects. Stimulation of T cells with coimmobilized anti-TCR-1 and ICAM-2 resulted in the induction of IL-2R (CD25), and anti-Tac (CD25) mAb inhibited this response suggesting the contribution of endogenously synthesized IL-2 during this stimulation. These results demonstrate that like its homologue ICAM-1, ICAM-2 also exerts a strong costimulatory effect during the TCR-initiated activation of T cells. The costimulatory effects generated by the CD11a/CD18:ICAM-2 interaction may be critical during the initiation of T cell activation by ICAM-1low APC.
Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, WA 98121.
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Damle
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Klussman
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Aruffo
D000938:Antigen-Presenting Cells / Q000502:physiology; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic / Q000235:genetics; D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D015815:Cell Adhesion Molecules / Q000502:physiology*; D005803:Genes, Immunoglobulin; D006801:Humans; D018799:Intercellular Adhesion Molecule-1; D007376:Interleukin-2 / Q000502:physiology; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015375:Receptors, Interleukin-2 / Q000502:physiology; D011993:Recombinant Fusion Proteins
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D015815:Cell Adhesion Molecules; C065289:ICAM2 protein, human; D007376:Interleukin-2; D016169:Lymphocyte Function-Associated Antigen-1; D009838:Oligodeoxyribonucleotides; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D018799:Intercellular Adhesion Molecule-1