Expressions of Very Late Antigen-6 and Vitronectin Receptor, and Their Interactions to Laminin and Vitronectin during Tonsillar B-Cell Activation

This study examined the expressions of a-subunits of very late antigen-6 (VLA-6; a6) and vitronectin receptor (VNR; αV) on tonsillar B cells and interactions between those integrins and their respective ligands, laminin (LM) and vitronectin (VN). α6 and αV were expressed on about 30 to 40% of tonsillar B cells. When purified tonsillar B cells were separated by a discontinuous Percoll gradient, the number of α6- and αV-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 expressions of a6 and aV and their adhesiveness to LM or VN decreased significantly. Increased proliferation of B cells was observed when tonsillar B cells were cultured with immobilized LM or VN. The results of immunohistological staining showed VLA-6, VNR, LM and VN in the follicular area. These results suggest that the expressions of VLA-6 and VNR on tonsillar B cells may be decreased during B cell activation, and the interaction between VLA-6, VNR, and LM, VN may give a costimulatory effect on B cell activation in the follicular area of the tonsi1.