INCREASED EXPRESSION OF NEUTROPHIL MRP8 AND MRP14 IS ASSOCIATED WITH VASCULAR ADHESION MOLECULE ACTIVATION AND DIFFERENTIAL LEUKOCYTE INFILTRATION IN DELAYED-TYPE HYPERSENSITIVITY SUGGESTING A PROINFLAMMATORY ROLE FOR S100 CALCIUM-BINDING PROTEINS

Cutaneous delayed type hypersensitivity (DTH) to methylated bovine ser um albumin (mBSA) exhibited early (4-24 h) neutrophil influx followed by a delayed increase in T lymphocytes (CD4(+);CD8(+)) and monocyte/ma crophage (F4/80(+)) infiltration. The mononuclear leukocyte response w as paralleled by a delayed increase in VLA4(+) cells. Vascular adhesio n molecule expression, assessed by immunocytochemistry and mRNA expres sion, showed increased ICAM-1 throughout the DTH reaction with a gradu al delayed increase in VCAM-1. Quantitative computer-assisted image an alysis of immunostained murine MRP8 and MRP14 demonstrated the unique intense cytoplasmic localization of these chemotactic proteins within intravascular and infiltrating neutrophils which diminished significan tly from 24-72 h; extracellular MRPS and MRP14 was also detectable. Ho wever, MRPS and MRP14 mRNA extracted from DTH lesions peaked around 24 h and persisted by 72 h. Subcutaneous challenge with mBSA antigen in control, non-sensitized mice resulted in a minor neutrophil response ( peak 4 h), which subsided by 24-72 h and consisted mainly of macrophag es and fibroblasts but not lymphocytes; expression of ICAM-1, VCAM-1 ( mRNA and protein) and VLA4 (protein) showed a slight but insignificant increase above levels found in normal control skin throughout the 0-7 2 h reaction. MRP8 and MRP14 protein delete expression was transiently elevated by 24 h but, unlike the DTH response, fell to baseline level s by 72 h whereas mRNA expression remained elevated. We conclude that continued synthesis and release of MRP8 and MRP14 from infiltrating ne utrophils may represent an important systemic and local mechanism for recruitment of neutrophils and monocytes into the DTH inflammatory sit e through bone marrow mobilization and chemotaxis of neutrophils and m onocytes.