Antibody and B7/BB1-mediated ligation of the CD28 receptor induces tyrosine phosphorylation in human T cells.
CD28 is an adhesion receptor expressed as a 44-kD dimer on the surface of a major subset of human T cells. The CD28 receptor regulates the production of multiple lymphokines, including interleukin 2 (IL-2), by activation of a signal transduction pathway that is poorly understood. Here we show that ligation of CD28 by a monoclonal antibody (mAb) or by a natural ligand, B7/BB1, induces protein tyrosine phosphorylation that is distinct from T cell receptor (TCR)-induced tyrosine phosphorylation. CD28-induced protein tyrosine phosphorylation was greatly enhanced in cells that had been preactivated by ligation of the TCR, or by pretreatment with phorbol esters. Rapid and prolonged tyrosine phosphorylation of a single substrate, pp100, was induced in T cells after interaction with B7/BB1 presented on transfected Chinese hamster ovary (CHO) cells. Anti-B7 mAb inhibited B7/BB1 receptor-induced tyrosine phosphorylation, indicating that B7-CD28 interaction was required. CD28-induced tyrosine phosphorylation was independent of the TCR because it occurred in a variant of the Jurkat T cell line that does not express the TCR. Herbimycin A, a protein tyrosine kinase inhibitor, could prevent CD28-induced tyrosine phosphorylation and CD28-induced IL-2 production in normal T cells. The simultaneous crosslinking of CD28 and CD45, a tyrosine phosphatase, could prevent tyrosine phosphorylation of pp100. These results suggest that specific tyrosine phosphorylation, particularly of pp100, occurs directly as a result of CD28 ligand binding and is involved in transducing the signal delivered through CD28 by accessory cells that express the B7/BB1 receptor. Thus, this particular form of signal transduction may be relevant to lymphokine production and, potentially may provide a means to study the induction of self-tolerance, given the putative role of the costimulatory signal in the induction of T cell activation or anergy.
Immune Cell Biology Program, Naval Medical Research Institute, Bethesda, Maryland 20889.
P
P
Vandenberghe
G J
GJ
Freeman
L M
LM
Nadler
M C
MC
Fletcher
M
M
Kamoun
L A
LA
Turka
J A
JA
Ledbetter
C B
CB
Thompson
C H
CH
June
D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000378:metabolism* / Q000502:physiology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D016227:Benzoquinones; D018106:CD28 Antigens; D006649:Histocompatibility Antigens / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000494:pharmacology; D047029:Lactams, Macrocyclic; D017493:Leukocyte Common Antigens; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011809:Quinones / Q000494:pharmacology; D011940:Receptor Aggregation; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017828:Rifabutin / Q000031:analogs & derivatives; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D016227:Benzoquinones; D018106:CD28 Antigens; D006649:Histocompatibility Antigens; D007376:Interleukin-2; D047029:Lactams, Macrocyclic; D010750:Phosphoproteins; D011809:Quinones; D011956:Receptors, Cell Surface; D017828:Rifabutin; D019000:Phosphotyrosine; D014443:Tyrosine; C020754:herbimycin; D017493:Leukocyte Common Antigens; D013755:Tetradecanoylphorbol Acetate