REQUIREMENT FOR C-X-C CHEMOKINES (MACROPHAGE INFLAMMATORY PROTEIN-2 AND CYTOKINE-INDUCED NEUTROPHIL CHEMOATTRACTANT) IN IGG IMMUNE COMPLEX-INDUCED LUNG INJURY

The C-X-C chemokines of the IL-8 family possess potent chemotactic act ivity for neutrophils, but their in vivo role in inflammatory response s is not well understood. In the IgG immune complex-induced model of a cute lung inflammatory injury in the rat we have evaluated the roles o f two rat chemokines, macrophage inflammatory protein-2 (MIP-2) and cy tokine-induced neutrophil chemoattractant (CINC). Both mRNA and protei n for MIP-2 and CINC appeared in a time-dependent manner after initiat ion of IgG immune complex deposition in lung. There exists a 69% homol ogy between the amino acid sequences for these proteins, and we found cross-reactivity between polyclonal Abs raised to these chemokines. By purifying the blocking Abs using double affinity methods (with Ag-imm obilized beads), this cross-reactivity was removed. Individually, anti -MIP-2 and anti-CINC Ab significantly reduced lung injury (as measured by I-125-labeled albumin leakage from the pulmonary vasculature) and reduced neutrophil accumulation in the lung (as determined by myeloper oxidase (MPO content) and neutrophil counts in bronchoalveolar lavage (BAL) fluids); however, no change in TNF-alpha levels in BAL fluids wa s found. Chemotactic activity in BAL fluids collected 2 h after injury from animals undergoing immune complex deposition could be shown to b e chiefly due to the combined contributions of MIP-2 (39%), CINC (28%) , and C5a (21%). When either MIP-2 or CINC was blocked in vivo, up-reg ulation of Mac-1 expression on neutrophils obtained from BAL fluids wa s significantly reduced. These data suggest that, in the model studied , both MIP-2 and CINC contribute significantly to the influx of neutro phils and their activation.