INCREASE IN HISTAMINE PRODUCTION BY INFLAMMATORY EXUDATE IN THE CHRONIC PHASE OF ALLERGIC INFLAMMATION IN RATS

In the air pouch-type allergic inflammation in rats, we reported that a sustained histamine production in the late phase is induced by a cyt okine-like factor, named histamine-production-increasing factor (HPIF) (1). Recently, we found another type of histamine-production-increasi ng factor in the pouch fluid at the chronic phase of air pouch-type al lergic inflammation. Although it did not increase histamine production by itself, it enhanced the HPIF-induced histamine production by rat b one marrow cells. It also increased GM-CSF-induced histamine productio n. The activity of this factor increased time-dependently from 3 to 7 days after the antigen challenge. Injection of the 5 day pouch fluid s ample containing this factor into the pouch 4 h after the antigen chal lenge increased histamine contents in the pouch fluid at 24 h, indicat ing that this factor enhances HPIF-induced histamine production in viv o. Biochemical analysis of the 5 day pouch fluid sample indicated that this factor is a heat-labile and trypsin-sensitive protein of which p i value and molecular weight are 7-8 and about 100 kDa, respectively.