Peripheral blood dendritic cells (BDC) are potent antigen-presenting lymphoid cells. In the present study, we have examined the in vitro adhesion of BDC to human umbilical cord venous endothelial cells (HUVEC) and studied the expression of CD molecules and oligosaccharide haptens on BDC and endothelial cells. Immunohistochemistry showed that BDC were strongly positive for antibodies against HLA-DR, CD11c, CD18, CD44 and CD54, and moderately positive for anti-CD11a, CD31, CD43 and CD58. In addition, BDC were moderately positive for anti-Sialyl Lewis a and strongly positive for anti-Sialyl Lewis x and CD77 (Gal alpha 1-4Gal beta 1-4Glc) Non-stimulated HUVEC were positive for anti-CD29, CD31 and CD77. An in vitro adhesion assay showed that only a small percentage of radiolabelled BDC bound to non-stimulated HUVEC (16.9 +/- 5.9%, mean +/- SD). Stimulation of the HUVEC with IL-1 for 4 h produced a significant increase (P < 0.002) in the percentage of radiolabelled BDC that bound to HUVEC (42.3 +/- 7.1%). Preincubation of HUVEC with antibodies against E-selectin (10 micrograms/ml) significantly inhibited (P < 0.02) the binding of radiolabelled BDC to activated HUVEC (32.2 +/- 1.3%) whereas preincubation of BDC with antibodies against CD54, CD18, CD11b, CD11c and Sialyl Lewis x did not produce any significant inhibition. Preincubation of BDC with Sialyl Lewis a antibody and with isotype-matched control antibodies did not affect the increased binding of BDC to IL-1-activated HUVEC. Thus, E-selectin seems to be involved in adhesion of BDC to IL-1-stimulated HUVEC.