Abstract
Employing the air pouch-type allergic inflammation model in rats, effects of inflammatory exudate on histamine production by bone marrow cells were examined in order to clarify the mechanism of histamine production at the site of allergic inflammation. The pouch fluid collected 8 h after the induction of allergic inflammation (the acute phase) increased histamine production by bone marrow cells. On the other hand, the pouch fluid collected 5 days after the antigen challenge (the chronic phase) showed no activity by itself, but enhanced the activity by the pouch fluid collected at the acute phase. These activities were due to proteinous factors that were produced at the acute phase and at the chronic phase, named histamine-production-increasing factor (HPIF) -I and HPIF-II, respectively. HPIF-I increased histidine decarboxylase (HDC) activity in bone marrow cells but HPIF-II did not. However, HPIF-II enhanced HDC activity stimulated by HPIF-I. The cooperative effect of HPIF-I and HPIF-II on histamine production was also observed in vivo. Isoelectric point and molecular weight of HPIF-II were estimated to be 7 to 8 and about 100 kD, respectively.
These results indicate that histamine production at the site of allergic inflammation might be regulated by at least two kinds of proteinous factors, HPIF-I and HPIF-II.
