B-LYMPHOCYTE BINDING TO E-SELECTIN AND P-SELECTIN IS MEDIATED THROUGHTHE DE-NOVO EXPRESSION OF CARBOHYDRATES ON IN-VITRO AND IN-VIVO ACTIVATED HUMAN B-CELLS

Cell adhesion to endothelium regulates the trafficking and recruitment of leukocytes towards lymphoid organs and sites of inflammation. This phenomenon is mediated by the expression of a number of adhesion mole cules on both the endothelium and circulating cells. Activation of end othelial cells (EC) with different stimuli induces the expression of s everal adhesion molecules (E- and P-selectins, ICAM-1, VCAM-1), involv ed in their interaction with circulating cells. In this report, we hav e studied the binding of nonactivated and activated B cells to purifie d E- and P-selectins. Activated but not resting B cells were able to i nteract with both selectins. This binding capacity of activated B cell s paralleled the induction of different carbohydrate epitopes (Lewis(x ), sialyl-Lewis(x), CD57 and CDw65) as well as other molecules bearing these or related epitopes in myeloid cells (L-selectin, alpha L beta 2 and alpha X beta 2 integrins, and CD35) involved in the interaction of different cell types with selectins. B cells infiltrating inflamed tissues like in Hashimoto's thyroiditis, also expressed these selectin -binding carbohydrates in parallel with the expression of E-selectin b y surrounding follicular dendritic cells. Moreover, the crosslinking o f these selectin-binding epitopes resulted in an increased binding of B cells to different integrin ligands. Thus, in addition to the involv ement of integrins, E- and P-selectins could play an important role in the interaction of B lymphocytes with the endothelium during B cell e xtravasation into lymphoid tissues and inflammatory foci as well as in their organization into lymphoid organs.