Characterization of a novel co-stimulatory molecule: a 155-160kD B cell surface protein provides accessory help to CD4+ T cells to proliferate and differentiate.
Optimal activation of T cells to clonally expand requires at least two distinct biological signals; one is generated by the interaction of the T cell receptor (TcR) with peptides bound to MHC molecules. The other signal(s) is (are) generated by a functionally defined event called the co-stimulatory pathway. We have characterized the co-stimulatory property of a murine B lymphocyte membrane protein (155-160 kD) on resting CD4+ T cells. The study involved the isolation of a 155-160 kD protein (B1) from the membranes of LPS-stimulated B cells. When reconstituted into lipid vesicles, B1 exerted a dose-dependent proliferative response to CD4+ T cells, resulting in the predominant secretion of IL-4 and IL-5 after cross-linking receptors with anti-CD3 mAb. This protein is a phosphoglycoprotein which gives a single spot on two-dimensional gel electrophoresis under reducing conditions and as a distinct peak on reverse phase-HPLC. The B1 binds to the T cell surface as is demonstrated by electron microscopic autoradiography and scanning electron microscopy, as well as competitive binding assays. It does not cross-react with antibodies directed against ICAM-1, LFA-1 alpha, B7, HSA and VCAM-1, suggesting the novelty of the protein. Activation of CD4+ T cells with B1 in the presence of anti-CD3 resulted in the translocation of protein kinase C (PKC). The B1 is barely detectable on the surface of resting B cells and digestion of this protein with V8 protease and peptide N-glycosidase F resulted in distinct protein bands on an autoradiogram.
Vinay
D S
DS
Institute of Microbial Technology, Sector 39A, Chandigarh 160 014, India.
Raje
M
M
Mishra
G C
GC
D000818:Animals; D000938:Antigen-Presenting Cells / Q000737:chemistry* / Q000276:immunology; D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002454:Cell Differentiation; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D007371:Interferon-gamma / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D015848:Interleukin-5 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D008565:Membrane Proteins / Q000737:chemistry / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D008970:Molecular Weight; D011493:Protein Kinase C / Q000378:metabolism
D007376:Interleukin-2; D015848:Interleukin-5; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D015847:Interleukin-4; D007371:Interferon-gamma; D011493:Protein Kinase C