Mechanisms Involved in the Binding of Thymocytes to Rat Thymic Dendritic Cells

摘要

The effects of monoclonal antibodies (mAbs) to cell-surface molecules, divalent cations,and various cell-signaling and metabolic inhibitors on the binding of thymocytes to ratthymic dendritic cells (TDC) were studied using a rosette assay. It was found that TDC/thymocyte adhesion was stronger and faster at 37℃ than at 4℃. Flow cytometric analysisdemonstrated that bound thymocytes were predominantly CD4+CD8+and CD4+CD8-, butin comparison to the phenotype of whole thymocytes, they were enriched in the matureTCRαβhisubset. The binding of thymocytes to TDC at 37℃ was almost completelydependent on Ca2+and Mg2+and partly on an intact cytoskeleton and calmodulin-dependentprotein kinase. The adhesion was independent of new protein synthesis andthe activities of protein kinases A and C, tyrosine kinases, as well as phosphotyrosine proteinphosphatases. The TDC/thymocyte adhesion at 37℃ was partly blocked by anti-LFA-1(WT.1), anti-CD18 (WT.3), and anti-ICAM-1 (1A29) mAb. MAbs to class II MHC (OX-3 andOX-6), CD4 (W3/25), CD8 (OX-8), and αβTCR (R73) stimulated the adhesion via an LFA-1-dependent pathway, whereas an anti-CD45 mAb (G3C5) stimulated the rosette formationindependently of LFA-1. MAbs to CD2 (OX-34), CD11b (ED7), CD11b/c (OX-42), andclass I MHC (OX-18) were without significant effects on the adhesion process.