Interaction and Immunological Effect of Very Late Antigen-4, 5, and Fibronectin in Tonsillar Lymphocytes and Their Relation to Age

We examined the expressions of a-subunits of very late antigen (VLA)-4 (oc4) and VLA-5 (a5) on tonsillar lymphocytes and the interaction between these integrin receptors and their ligand, fibronectin (FN). Immunohistological and flow cytometric analyses showed that a 4 and a 5 were expressed in the lymphoid follicle and were positive on about 10% each of T cells and on 55% and 35% of B cells. When tonsillar B cells were separated by a discontinuous Percoll gradient, the number of a4- and 5-positive cells decreased as the cell density went down, while the number of activated cells went up. After in vitro activation of tonsillar B cells by Staphylococcus aureus Cowan I strain (SAC), the expression of a5 and the adhesiveness to FN decreased. the increased proliferation of B cells was observed when tonsillar B cells were cultured with immobilized FN. the expressions of α-subunits of VLA-4 and VLA-5 on tonsillar T and B lymphocytes increased with age. These results suggest that: i) B cell activation may cause decreased expressions of VLA-4 and -5, which gives a costimulatory effect on B cell activation itself again in cooperation with FN, ii) Increased expressions of VLA-4 and -5 on tonsillar lymphocytes with age may be related to regional immune response of the palatine tonsils. very late antigen-4 (VLA-4), very late antigen-5 (VLA-5), fibronectin (FN), tonsillar lymphocyte.