LAM-1 LEU-8 ANTIGEN IS EXPRESSED ON PORTAL, BUT NOT ON LOBULAR INTRAHEPATIC MONONUCLEAR-CELLS IN INFLAMMATORY LIVER-DISEASE

The expression of the selectin receptor LAM-1/Leu 8 was analysed in no rmal and in inflamed liver tissue, and its expression on mononuclear i nflammatory cells was correlated with their topographical distribution in various compartments of the inflamed liver, in order to obtain new insights on possible molecular mechanisms involved in the traffic of mononuclear inflammatory cells throughout the diseased hepatic parench yma. In normal liver tissue, few scattered mononuclear cells in portal and lobular parenchyma corresponded to both CD4+ and CD8+, as well as to CD45RA+ (2H4+) naive and CD45RO+ (UCHL1+) memory T cells, and were LAM-1/Leu 8+. In acute and chronic inflamed liver biopsies, CD45RO+ ( UCHL1+) CD4+ and CD8+ memory T cells largely predominated in both port al and lobular parenchyma. The expression of LAM-1/Leu 8 antigen on th ese memory T cells varied according to their localization in the liver parenchyma, and it was not correlated with specific aetiological caus es. In acute hepatitis, the vast majority of T lymphocytes were LAM-1/ Leu 8-. In chronic active hepatitis, memory T cells in portal tracts e xpressed LAM-1/Leu 8, whereas virtually all intralobular T cells accum ulating in areas of periportal and intralobular inflammation were LAM- 1/Leu 8-. In chronic persistent hepatitis, the LAM-1/Leu 8+ T cells la rgely predominated among the numerous mononuclear inflammatory cells w ithin enlarged portal tracts, whereas LAM-1/Leu 8- T cells were restri cted to areas of intralobular 'spotty' inflammation. Therefore, two ph enotypical populations can be recognized among the memory T cells in i nflamed liver tissue, according to their topographical localization: L AM-1/Leu 8+ T cells predominating in portal tracts, and LAM-1/Leu 8- T cells predominating in the lobular parenchyma. These data show that d uring their migration through the inflamed liver parenchyma, memory T lymphocytes undergo phenotyical changes (LAM-1/Leu 8 shedding) accordi ng to their localization in different liver compartments (portal tract s vs. lobular parenchyma), suggesting multiple cellular and molecular mechanisms involved in the regulation of the leucocyte traffic through inflamed liver tissue.