title: The requirement for lymphocyte function-associated antigen 1 in homotypic leukocyte adhesion stimulated by phorbol ester.
abstract: Lymphocytes become adherent and aggregate after stimulation with phorbol esters such as PMA. Time-lapse video showed that aggregating cells were motile and exhibited vigorous pseudopodial movements. Adhesion sites were initiated between pseudopodia of neighboring cells, and then moved to the uropod. PMA-stimulated aggregation by EBV-transformed B cell lines, SKW-3 (a T cell line), differentiated U937 (a monocytic line), and blood lymphocytes was inhibited by mAbs to LFA-1. A number of different mAb to the LFA-1 alpha and beta subunits and F(ab')2 and Fab' fragments inhibited aggregation. Furthermore, lymphoblasts from normal individuals, but not from LFA-1-deficient patients, aggregated in response to PMA. These findings suggest LFA-1 is critically involved in stimulated lymphocyte adhesion. LFA-1 expression was not increased by PMA stimulation, showing that other mechanisms regulate LFA-1-dependent adherence. LFA-1-deficient patient cells were able to coaggregate with LFA-1+ cells, showing that aggregation is not mediated by like-like interactions between LFA-1 molecules on opposite cells. Aggregation was Mg+2-dependent, inhibited by cytochalasin B, and was reversed when LFA-1 mAb was added to preformed aggregates. Previous findings suggesting that LFA-1 is important in a wide variety of leukocyte functions are elucidated by this work, which shows that LFA-1 is a general leukocyte cell adhesion molecule, the activity of which is regulated by cell activation.
mesh_terms: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000276:immunology*; D002413:Cations, Divalent / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D006801:Humans; D007152:Immunologic Capping / Q000187:drug effects; D007962:Leukocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D016169:Lymphocyte Function-Associated Antigen-1; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology; D016177:Macrophage-1 Antigen; D009000:Monocytes / Q000166:cytology / Q000276:immunology; D010704:Phorbols / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D002413:Cations, Divalent; D016169:Lymphocyte Function-Associated Antigen-1; D016177:Macrophage-1 Antigen; D010704:Phorbols; D013755:Tetradecanoylphorbol Acetate