title: A novel anti-rat CD18 monoclonal antibody triggers lymphocyte homotypic aggregation and granulocyte adhesion to plastic: different intracellular signaling pathways in resting versus activated thymocytes.
abstract: We have raised a monoclonal antibody (mAb), NG2B12, directed against rat CD18, capable of inducing lymphocyte homotypic adhesion and granulocyte adherence to plastic. NG2B12-induced aggregation is temperature sensitive and requires metabolic energy, an intact cytoskeleton and the presence of Mg2+, but is independent of protein synthesis. Ca2+ is not only dispensable but exerts a suppressive effect on the NG2B12-induced adhesion. The adhesion is readily observed in thymocytes and concanavalin A blasts of thymocytes and splenocytes but is very weak in resting spleen and lymph node cells. NG2B12 also enhances phorbol 12-myristate 13-acetate (PMA)-induced aggregation in an additive fashion. The NG2B12-induced homotypic adhesion is mediated by LFA-1. mAb against ICAM-1 completely inhibited the induced adhesion of activated cells but inhibited only partially and in a time-dependent manner the adhesion of resting thymocytes. The activation of protein phosphatases 1 and 2A (as assessed by the use of okadaic acid) is necessary for the NG2B12-induced adhesion of both resting and activated thymocytes. In contrast, H-7 (an inhibitor of protein kinase C and A), substantially suppressed the adhesion of resting thymocytes, whereas W-7 (an inhibitor of calmodulin-dependent protein kinase) inhibited the adhesion of activated thymocytes. NG2B12 induces both adherence to plastic and homotypic aggregation of granulocytes; the events being blocked by anti-CD18 (WT.3) and anti-CD11b/CD11c (OX-42) mAb, augmented by okadaic acid and not modified by H-7 and W-7. Additionally, we have demonstrated that NG2B12 and PMA employ distinct intracellular signaling pathways in inducing adhesion of both thymocytes and granulocytes.
authors.affiliation: Institute of Medical Research, Military Medical Academy, Belgrade, Yugoslavia.
authors.forename: M D
authors.initials: MD
authors.lastname: Pavlović
authors.forename: M
authors.initials: M
authors.lastname: Colić
authors.forename: N
authors.initials: N
authors.lastname: Pejnović
authors.forename: T
authors.initials: T
authors.lastname: Tamatani
authors.forename: M
authors.initials: M
authors.lastname: Miyasaka
authors.forename: A
authors.initials: A
authors.lastname: Dujić
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D015703:Antigens, CD / Q000276:immunology*; D018821:CD18 Antigens; D002448:Cell Adhesion / Q000276:immunology*; D015815:Cell Adhesion Molecules / Q000502:physiology; D002449:Cell Aggregation / Q000276:immunology*; D002478:Cells, Cultured; D003124:Colorimetry; D005260:Female; D006098:Granulocytes / Q000276:immunology; D018799:Intercellular Adhesion Molecule-1; D007962:Leukocytes / Q000276:immunology*; D008213:Lymphocyte Activation / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology; D008214:Lymphocytes / Q000276:immunology; D051381:Rats; D015398:Signal Transduction / Q000276:immunology*; D013950:Thymus Gland / Q000166:cytology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018821:CD18 Antigens; D015815:Cell Adhesion Molecules; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1