ROLE OF A SIALYL LEWIS(X)-LIKE EPITOPE SELECTIVELY EXPRESSED ON VASCULAR ENDOTHELIAL-CELLS IN LOCAL SKIN INFLAMMATION OF THE RAT

The role of the inducible L-selectin ligand was studied in complement- dependent acute dermatitis in rats. Although mAbs against typical sial yl Lewis(x) (CSLEX-1 and SNH-3) did not react with skin venules, a sia lyl Lewis(x)-like epitope defined by mAb 2H5 (2H5-Ag) was de novo expr essed on the endothelial cells of skin venules in the area of inflamma tion. Expression of 2H5-Ag increased concomitantly with the progressio n of inflammation. 2H5-Ag was identified at the 75-, 150-, and 180-kDa bands when inflammatory skin tissue was analyzed by Western blotting. In contrast, P- and E-selectins were not detectable. The role of 2H5- Ag in this model was studied in in vitro and in vivo methods. First, 2 H5 was iv injected 15 min before induction of dermatitis. 2H5 bound to skin venules and significantly reduced the neutrophil infiltration an d plasma protein leakage. In contrast, CSLEX-1, mAb ARP2-4 (P-selectin blocker), or mAb ARE-5 (E-selectin blocker) had no effects. Second, a dhesion of isolated rat neutrophils to the inflammatory skin section w as inhibited significantly when the sections, but not neutrophils, wer e preincubated with 2H5. Third, fluorescein-labeled normal rat neutrop hils were injected into a rat 10 h after induction of dermatitis. The number of labeled neutrophils infiltrated into the inflammatory site w as reduced significantly when they were preincubated with HRL-3 (block ing mAb against rat L-selectin), but not with 2H5 or HRL-4 (nonblockin g mAb against rat L-selectin). These data show that de novo expressed 2H5-Ag/L-selectin adhesion pathway contributes to the development of a cute complement-dependent inflammation in the skin.