BACTERIAL-CELL WALL PRODUCTS INCREASE MONOCYTE HLA-DR AND ICAM-1 WITHOUT AFFECTING LYMPHOCYTE CD18 EXPRESSION

Bacterial cell wall products such as lipopolysaccharide (LPS) and mura myl dipeptide (MDP) have the capacity to enhance immune responses to a ntigens. The expression of surface class II major histocompatibility a ntigens and the costimulatory receptors CD18 and CD54/ICAM-1 (intercel lular adhesion molecule) was used to evaluate the comparative influenc e of these immunostimulators On monocytes, both LPS and MDP increased the expression of human leukocyte antigen (HLA)-DR (maximal at 6 hr), CD18 (maximal at 1-3 hr), and ICAM-1 (maximal at 18-24 hr for LPS and 12 hr for MDP) without increasing the production of superoxide. MDP-in duced ICAM-1 expression on monocytes returned to baseline values after 12 hr. On lymphocytes, only LPS increased ICAM-1 (after 18 hr) withou t affecting CD18, and a differential analysis demonstrated a generaliz ed ICAM-1 upregulation in lymphocyte subsets after 18 hr: the most pro nounced effect was measured in natural killer cells, followed by CD8() T cells, B cells, and CD4(+) T cells. MDP did not alter ICAM-1 or CD 18 expression on lymphocytes. These similar but smaller effects of MDP may, in part, explain the lesser toxicity of MDP when compared to LPS . (C) 1997 Academic Press.