INHIBITORY-ACTION OF SULFATIDE, A PUTATIVE LIGAND FOR L-SELECTIN, ON B-CELL PROLIFERATION AND IG PRODUCTION

The interaction of L-selectin and its ligand is widely accepted to med iate leukocyte rolling and adhesion on the endothelial surface, Althou gh L-selectin is ubiquitously expressed on lymphoid cells, its role in execution of lymphocyte functions is unknown, By flow cytometric anal ysis using mAb specific for sulfatide, a putative ligand for L-selecti n, we found that sulfatide was selectively expressed on B cells, but n ot on T cells, To elucidate the involvement of L-selectin and its liga nd in B cell activation, the present study was undertaken to investiga te effects of sulfatide on T cell-dependent and -independent Ig produc tion by B cells. In pokeweed mitogen-stimulated cultures, addition of sulfatide resulted in almost complete inhibition of Ig production by B cells in the presence of memory CD4(+) T cells, whether L-selectin-po sitive or -negative, A similar inhibition of Ig production by sulfatid e was found when B cells were stimulated with Staphylococcus aureus Co wan I and IL-2, Unlike sulfatide, a desulfated form of sulfatide, gala ctosylceramide, did not show any effects on Ig production by B cells, Maximal inhibition of Ig production was observed when sulfatide was ad ded at the early period of culture. Sulfatide suppressed effectively p roliferation of B cells, but not of T cells, Sulfatide competed the bi nding of anti-l-selectin mAb to B cells, suggesting it could interfere B cell activation by blocking L-selectin function, The results sugges t a novel role of the L-selectin/its ligand system in the initiation o f B cell activation.