The in vivo quantitation and kinetics of rabbit neutrophil leukocyte accumulation in the skin in response to chemotactic agents and Escherichia coli.

This report describes the in vivo quantitation of neutrophil accumulation at inflammatory sites in rabbits by employing 51Cr-labeled autologous rabbit blood neutrophils. These labeled neutrophils circulated with a half of 3.2 to 3.8 hours. They were found to localize with great specificity at skin sites injected intradermally with zymosan-activated plasma, synthetic chemotactic peptides (e.g., N-formyl methionyl leucyl phenylalanine), Escherichia coli-derived chemotactic factors, or whole E. coli. Contrary to reports utilizing in vitro assays, under in vivo conditions the synthetic chemotactic peptides caused significantly less neutrophil accululation than zymosan-aulation by high concentrations of N-formyl methionyl leucyl phenylalanine was observed. Kinetic studies of the accumulation of labeled leukocytes in the skin in response to intradermal injection of formalin-killed E. coli were performed. Nearly all of the leukocytes accumulated during the first 4 hours after E. coli injection with a peak rate of accumulation between 2 and 3 hours. Essentially no additional localization of leukocytes occurred at lesions which were 6, 8, or 24 hours old. These results demonstrate that 51Cr-labeled rabbit blood neutrophils can be utilized to quantitate the degree of neutrophil accumulation in inflammatory reactions as well as to study the hour by hour kinetics of this accumulation.