DIFFERENTIAL EXPRESSION OF T-CELL ADHESION MOLECULES AND LFA-1-DEPENDENT INTERCELLULAR-ADHESION IN HGCL2-INDUCED AUTOIMMUNITY AND IMMUNE SUPPRESSION

Exposure of Brown Norway (BN) rats to HgCl2 induces Th2-mediated syste mic autoimmunity. In contrast, in Lewis rats, HgCl2 induces immune sup pression, mediated by CD8(+) T cells. HgCl2 was previously found to en hance expression of LFA-1, ICAM-1 and CD134 (OX40) on T cells in BN ra ts. In the present study, T cells from Lewis rats were studied at day 4 after injection of HgCl2. CD8(+) T lymphoblasts were significantly i ncreased, which were predominantly CD45RC(hi), and which showed enhanc ed LFA-1 expression. Furthermore, CD4(+)CD45RC(hi) T cells showed incr eased numbers of ICAM-1(+) cells, whereas expression of CD134 and CD26 was relatively decreased in CD4(+) T lymphoblasts. Ex vivo experiment s demonstrated that HgCl2-exposure of BN rats, but not of Lewis rats, significantly enhances PMA [phorbol 12-myristate 13-acetate]-induced l ymphocyte aggregation, mediated by LFA-1 and ICAM-1. In conclusion, Hg Cl2-injected Lewis rats show early signs of T-lymphocyte activation, p redominantly on CD8(+) cells. Strain-dependent effects of HgCl2 on cel l adhesion molecules and expression of CD134 may play an important rol e in development of either autoimmunity or immune suppression.