HUMAN T-LYMPHOCYTES BIND TO GERMINAL-CENTERS OF HUMAN TONSILS VIA INTEGRIN ALPHA-4 VCAM-1 AND LFA-1/ICAM-1 AND LFA-1/ICAM-2/

Binding of T lymphocytes within the different compartments of the seco ndary lymphoid organs is crucial for the function of the cellular and the humoral immune response. It is still not known which adhesion mole cules guide T cells to the distinct areas of the lymphoid microenviron ment. In the current study an in situ adhesion assay was used to defin e the receptors for binding of T cells to human tonsils. The T cell li nes Jurkat and MOLT-4 and normal, activated T cells were found to bind exclusively to germinal centers. Jurkat cells used the receptor pair integrin-alpha 4 (VLA-4 alpha)/VCAM-1, whereas activated MOLT-4 cells and normal T cells bound via both adhesion pathways, namely via integr in-alpha 4/VCAM-1 and LFA-1/ICAM-1 and -2. It is suggested that these adhesion mechanisms are involved in the migration of T cells into the germinal centers of secondary lymphoid organs and that they influence the selection of B cells by apoptosis.