title: Regulation of the tyrosine kinase-dependent adhesion pathway in human lymphocytes through CD45.
abstract: Cell-cell adhesive interactions involve numerous receptor/ligand interactions that play a crucial role in the development of immune function. Engagement of multiple cell-surface molecules on B lymphocytes generates intracellular signals through a tyrosine kinase-dependent pathway that activates cell-surface adhesion receptors and thereby induces homotypic cell-cell adhesion. Homotypic adhesion is mediated in part through LFA-1/ICAM-1 and other heretofore unknown adhesion receptors. In this study, evidence of a regulatory role for CD45 in the induction of homotypic adhesion is suggested. A new mAb (HAB-1) was developed that inhibits homotypic adhesion in B cell lines induced through MHC class I and class II, CD19, CD20, CD21, CD40, and Leu-13 cell-surface molecules. Although binding of this mAb strongly inhibited cell-surface Ag-induced homotypic adhesion at mAb concentrations as low as 0.1 microgram/ml, it exhibited no effect on homotypic adhesion induced by phorbol esters. Binding of the HAB-1 mAb to lymphocytes altered the pattern of cellular protein tyrosine phosphorylation, but did not have a global inhibitory effect on cell activation because it did not have major effects on the growth of mitogen-activated lymphocytes. Immunoprecipitation studies revealed that the HAB-1 mAb identified an epitope present on all isoforms of CD45. The HAB-1 mAb may identify a unique epitope of CD45 because this mAb had a unique staining pattern when assessed by indirect immunofluorescence staining. The HAB-1 mAb was similar to some other CD45 mAb that have the capacity to amplify CD2-induced proliferation of blood lymphocytes. However, only 1 of 12 other anti-CD45 mAb tested had a similar inhibitory effect on adhesion. Homotypic adhesion of lymphocytes may therefore be governed by a regulatory system of cell-surface molecules that generate positive and negative signals that either trigger adhesion or, like CD45, directly down-regulate adhesion. This highlights the significance of adhesive events that result from surface molecules being engaged by their natural ligands during lymphocyte activation.
authors.affiliation: Division of Tumor Immunology, Dana-Farber Cancer Institute, Boston, MA.
authors.forename: N
authors.initials: N
authors.lastname: Wagner
authors.forename: P
authors.initials: P
authors.lastname: Engel
authors.forename: T F
authors.initials: TF
authors.lastname: Tedder
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology; D001666:Binding Sites, Antibody; D018801:CD2 Antigens; D002448:Cell Adhesion / Q000276:immunology; D002460:Cell Line; D000939:Epitopes / Q000032:analysis; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000494:pharmacology; D007145:Immunoglobulin kappa-Chains / Q000096:biosynthesis / Q000494:pharmacology; D017493:Leukocyte Common Antigens / Q000737:chemistry / Q000276:immunology / Q000502:physiology*; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000201:enzymology* / Q000276:immunology / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000276:immunology* / Q000502:physiology; D011971:Receptors, Immunologic / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D018801:CD2 Antigens; D000939:Epitopes; D007075:Immunoglobulin M; D007145:Immunoglobulin kappa-Chains; D011971:Receptors, Immunologic; D011505:Protein-Tyrosine Kinases; D017493:Leukocyte Common Antigens