CHARACTERIZATION OF LEUKOCYTE-DERIVED NEUTROPHIL CHEMOTACTIC FACTOR-II AND ITS POSSIBLE ROLES IN NEUTROPHIL INFILTRATION IN ALLERGIC INFLAMMATION IN RATS

This study sought to clarify the responsible chemotactic factor for ne utrophils in allergic inflammation in rats. When the leukocytes collec ted from the pouch fluid 4 h after injection of the antigen solution i nto the air pouch were incubated, the neutrophil chemotactic activity in the conditioned medium increased time-dependently with higher level s for the leukocytes from the immunized rats than the nonimmunized one s. The chemotactic activity did not result from cytokine-induced neutr ophil chemoattractant (CINC) because CINC concentrations in the condit ioned medium were low Neutrophil chemotactic factors in the conditione d medium were separated by isoelectric focusing into two factors, leuk ocyte-derived neutrophil chemotactic factor (LDNCF)-1 and LDNCF-2. The activity of LDNCF-2 was more than 75% of the total chemotactic activi ty in the conditioned medium. LDNCF-2 was purified by gel chromatograp hy and reverse-phase HPLC. The N-terminal amino acid sequence (1-20) o f the purified LDNCF-2 was identical to the 32-51 amino acid sequence of the pro-form of rat macrophage inflammatory protein (MTP)-2. Higher levels of MIP-2 mRNA in the leukocytes from the immunized rats than t hat from the non-immunized rats were proved by the reverse transcripti on-polymerase chain reaction. In vivo, concentrations of CINC in the p ouch fluid were low, and did not represent the chemotactic activity in the pouch fluid. These results suggest that LDNCF-2 (MIP-2) is an imp ortant chemotactic factor for neutrophils in the allergic inflammation in rats.