DIFFERENTIAL EXPRESSION OF CELL-ADHESION MOLECULES IN THE FUNCTIONAL COMPARTMENTS OF LYMPH-NODES AND TONSILS

Aims-To analyse the topographical distribution of adhesion molecules i nvolved in lymphocyte recirculation in human lymph nodes and tonsils. The study focused on the expression of LECAM-1 (CD62L), VLA-alpha 4 (C D49d), VLA-beta 1 (CD29), LFA-1 alpha L (CD11a), LFA-beta 2 (CD18), VC AM-1 (CD 106), ICAM-1 (CD54), and H-CAM (CD44). Methods-Reactive lymph nodes and palatine tonsils were studied using immunofluorescence meth ods with fluorescein isothiocyanate (FITC) labelled monoclonal antibod ies directed against cell adhesion molecules. To investigate the expre ssion patterns of these molecules in the T and B cell populations, dou ble labelling experiments were performed using Texas Red labelled anti bodies against CD2 or CD19, respectively. The images from each fluoroc hrome were then simultaneously analysed using a laser scanning confoca l microscope. Results-LECAM-1, VLA-alpha 4 and H-CAM were predominantl y expressed by mantle zone B cells, VCAM-1 and ICAM-1 by germinal cent re cells, most of which exhibited a reticular staining pattern suggest ive of follicular dendritic whereas LFA-1 alpha L and LFA-beta 2 mainl y found in extrafollicular and germinal centre T cells. All high endot helial venules expressed VLA-beta 1 and ICAM-1, whereas VCAM-1 was pre sent in only a few, with variable intensity. Conclusions-The data show that all of these adhesion molecules are differently distributed with in the distinct functional microenvironments of both organs. The diffe rences observed in the expression patterns among the B and T cells bel onging to different compartments probably depend on the momentum of ce ll traffic, the stage of maturation/activation, as well as on their fu nctional role in the immune response.