EXPRESSION OF THE CHEMOKINE N51 KC IN THE THYMUS AND EPIDERMIS OF TRANSGENIC MICE RESULTS IN MARKED INFILTRATION OF A SINGLE CLASS OF INFLAMMATORY CELLS/

Transgenic mice expressing the chemokine N51/KC in thymus, skin, and t ongue showed a marked infiltration of a single class of inflammatory c ells (neutrophils) in the sites of transgene expression. In the thymus , neutrophils were most numerous in the cortex and juxta-medullary reg ions, often forming aggregates or clusters. A similar, but less intens e, neutrophilic infiltrate occurred in close proximity to the epiderma l basal layer of the tongue and skin. No morphologic evidence of injur y was observed in the thymus, skin, or tongue of these transgenic mice , indicating that N51/KC expression induces recruitment but not inflam matory activation of neutrophils. The lack of activation in the thymus resulted in a large senescent neutrophilic population that was phagoc ytosed by thymic macrophages and epithelial-reticular cells. These res ults indicate that N51/KC is a neutrophil chemoattractant in vivo and establish these transgenic mice as effective models to study the pheno mena of recruitment and clearance of neutrophils, events that are crit ical for the initiation and resolution of the inflammatory response.