T cell stimulation via CD47: agonistic and antagonistic effects of CD47 monoclonal antibody 1/1A4.
CD47/integrin-associated protein has been extensively studied on various cell types. The function of CD47 on T cells, however, remained poorly understood. We demonstrate here that our CD47 mAb 1/1A4 has both inhibitory as well as costimulatory effects in terms of T cell activation. Soluble, not cross-linked, CD47 mAb 1/1A4 blocks allogeneic MLRs. This effect is predominantly observed with suboptimal numbers of stimulator cells. In contrast, cross-linking of CD47 in the presence of CD28 mAb or phorbol ester induces vigorous T cell proliferation that is sensitive to cyclosporin A. Cross-linking, but not immobilization, of the CD47 mAb 1/1A4 is an essential requirement for the CD28- or phorbol ester-dependent induction of T cell mitogenesis. Furthermore, CD47 mAb 1/1A4 induces T cell proliferation when coimmobilized with a CD3 mAb to the same surface. Ligation with cross-linked 1/1A4 mAb induces an increase in intracellular free calcium levels and leads to tyrosine phosphorylation of various cellular proteins and, in the presence of suboptimal concentrations of plate-bound CD3 mAb, to enhanced IL-2 promotor activity in T cells. Furthermore, we present evidence that upon cross-linking of CD47 with mAb 1/1A4, purified T cells acquire responsiveness for several T cell growth factors. IL-1beta and/or IL-6 dramatically augment this CD47-induced cytokine responsiveness. Our results suggest that the novel activation pathway via CD47 might be critically involved in Ag-dependent and Ag-independent T cell functions.
Waclavicek
M
M
Institute of Immunology, University of Vienna, Austria.
Majdic
O
O
Stulnig
T
T
Berger
M
M
Baumruker
T
T
Knapp
W
W
Pickl
W F
WF
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology*; D018106:CD28 Antigens / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D051928:CD47 Antigen; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000276:immunology*; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D007959:Lymphocyte Culture Test, Mixed; D013601:T-Lymphocytes / Q000276:immunology*; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018106:CD28 Antigens; D017252:CD3 Complex; D051928:CD47 Antigen; C497894:CD47 protein, human; D002352:Carrier Proteins; D007375:Interleukin-1; D015850:Interleukin-6; D002118:Calcium