A lymphocyte-derived histamine-releasing factor in asthmatic patients. III. Further studies.

Peripheral blood lymphocytes from atopic asthmatic patients cultured overnight (16 hours) produced a novel lymphokine-histamine releasing factor (HRF) in the culture supernatant. Activity of this lymphokine has been tested in the basophil histamine release test. Supernatant from unstimulated lymphocytes released 29% histamine from basophils. A short incubation of lymphocytes with skin test-positive allergens (grass, mite) enhanced the generation of HRF. Skin test-negative allergens had no effect. HRF appeared in the supernatant as early as four hours after the start of the culture and its production level remained high even at 48 hours. Gel-filtration with Sephadex G-75 revealed an apparent molecular weight for HRF in the range of 10,000 to 15,000. HRF is relatively heat stable at 56 degrees C.