Signalling through CD28 T-cell activation pathway involves an inositol phospholipid-specific phospholipase C activity.
Stimulation of the human T-cell line, Jurkat, by a monoclonal antibody (mAb) directed against the CD28 molecule leads to sustained increases in intracellular levels of Ca2+ ([Ca2+]i); the initial rise in Ca2+ comes from internal stores, followed by Ca2+ entry into the cells. The CD28 molecule also appears to activate polyphosphoinositide (InsPL)-specific phospholipase C (PLC) activity in Jurkat cells, as demonstrated by PtdInsP2 breakdown, InsP3 and 1,2-diacylglycerol generation and PtdIns resynthesis. We also observed that interleukin-2 (IL2) production induced via CD28 triggering was sensitive to a selective protein kinase C inhibitor. Of the four other anti-CD28 mAbs (CD28.2, CD28.4, CD28.5, CD28.6) tested, only one (CD28.5) was unable to generate any InsPL-specific PLC or IL2 secretion. However, the cross-linking of cell-bound CD28.5 with anti-mouse Ig antibodies led to an increase in [Ca2+]i. CD28-molecule clustering in itself appears to be a sufficient signal for induction of PLC activity.
Nunes
J
J
Unité de Cancérologie et Thérapeutique Expérimentales U 119 INSERM, Marseille, France.
Klasen
S
S
Franco
M D
MD
Lipcey
C
C
Mawas
C
C
Bagnasco
M
M
Olive
D
D
D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000378:metabolism*; D018106:CD28 Antigens; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003432:Cross-Linking Reagents; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis; D008213:Lymphocyte Activation; D008301:Maleimides / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D018106:CD28 Antigens; D003432:Cross-Linking Reagents; D007211:Indoles; D007376:Interleukin-2; D008301:Maleimides; D011956:Receptors, Cell Surface; D011493:Protein Kinase C; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; C070515:bisindolylmaleimide I; D002118:Calcium