The role of neutrophils in acute and chronic inflammation in rats.

The effect of neutropenia on acute and chronic inflammatory oedema in rats was assessed using histamine, carrageenan and Freund's complete adjuvant as inducers. Neutropenia (about 85% reduction in peripheral blood neutrophil count) was induced with intraperitoneal administration of 2.5 mg/kg methotrexate for three consecutive days. Acute paw oedemas induced with carrageenan and Freund's complete adjuvant, but not that induced by histamine, were significantly decreased in neutropenic animals compared with controls. In adjuvant-induced chronic knee swelling (Adjuvant arthritis), neutropenia produced small, statistically non-significant, suppressive effect. In contrast, it significantly suppressed adjuvant-induced chronic paw swelling, although suppression was observed only in the late phase component of the swelling. The results suggest that neutrophils are involved in certain acute and chronic inflammatory responses but not in others.