Figure 1.
l-histidine decarboxylase (HDC) activity and histamine production by the leucocytes infiltrating the pouch fluid. (a) Leucocytes were collected from the pouch fluid of the immunized and the non-immunized rats 8 hr (open columns) and 24 hr (hatched columns) after injection of the antigen solution into the air pouch. Leucocytes (1·0 × 108 cells/ml) from each rat were sonicated, centrifuged and HDC activity in the supernatant fraction was determined as described in the Materials and methods. HDC activity is expressed as pmol/min/mg of protein. Values represent the mean ± SEM of three rats. Statistical significance: *P < 0·05 versus the corresponding non-immunized group. (b) Infiltrating leucocytes (4·0 × 106 cells/well) obtained from the immunized and the non-immunized rats 8 hr after injection of the antigen solution into the air pouch were cultured for 24 hr at 37° in Eagle’s minimal essential medium (EMEM) containing 10% fetal bovine serum (FBS), 5·0 mm l-histidine and 0·02 mm pyridoxal 5′-phosphate. Histamine contents in the conditioned medium were measured as described in the Materials and methods. Values represent the mean ± SEM of four rats. Statistical significance: ***P < 0·001 versus the non-immunized group.