Lymphocyte recognition of lymph node high endothelium: adhesive interactions determining entry into lymph nodes

Our interpretation of these results is that lymphocyte surface HEBF is composed of high endothelial adhesion molecules which mediate cell-cell interactions that result in lymphocyte entry from blood into lymph nodes. The evidence that anti-HEBF antibody does not interfere with lymphocyte entry into PP is intriguing, since migration into this tissue as well as LN, occurs via HEV. This suggests that high endothelial cells differ in LN and PP at least with respect to the specificity of surface molecules involved in lymphocyte adherence. It could be that separate lymphocyte subpopulations express receptors for these two types of high endothelium. If this explanation is correct, then cells negatively selected using this antibody should be capable of binding to HEV of PP but not HEV of LN. However, if receptors for both high endothelial types are present on the same lymphocyte, then it is unlikely that such selection would yield cells exhibiting tissue specificity. Our observations are consistent with previous findings which suggested that high endothelial cells of mouse LN and PP exhibit differences in lymphocyte binding properties. For example, it has been reported that certain murine lymphomas bind to HEV of either peripheral LN or PP and that, to a limited degree, this preference is a property of most B and T cells [Butcher et al, 1980; Stevens et al, 1982]. Thymus and bone marrow cells show only low levels of HEV binding and less than 10% of such cells react with anti-HEBF antibody. During differentiation lymphocytes appear to acquire surface components which mediate high endothelial adhesion and this event is associated with the appearance of surface molecules recognized by anti-HEBF antibody. This suggests that it is the expression of these surface molecules during differentiation which confers high endothelial recognition properties on lymphocytes and that this mechanism plays a role in adhesive interactions leading to entry of both T and B cells into LN.