Bacterial antigens stimulate the production of histamine releasing factor (HRF) by lymphocytes from intrinsic asthmatic patients.

Lymphocyte from 12 intrinsic asthmatic patients and 10 healthy controls were studied for their capability to produce histamine releasing factor (HRF) in vitro. Spontaneous HRF production was measured by culturing the lymphocytes alone for 20 h. In another set of experiments lymphocytes were first preincubated separately with phytohaemagglutinin, antigens of Haemophilus influenzae, Streptococcus viridans, Staphylococcus sp. and Neisseria catarrhalis for 4 h then carefully washed three times and cultured alone for an additional 16 h. Cell-free supernatant was assayed for histamine releasing activity using basophils from healthy donors. It was observed that lymphocytes from intrinsic asthmatic patients spontaneously produced HRF. The production of this lymphokine was enhanced following preincubation of lymphocytes with phytohaemagglutinin or bacterial antigens. Results of skin test with bacterial antigens did not correlate with the magnitude of the production of HRF by lymphocytes. At gel chromatography over Sephadex G-75 bacterial antigen-stimulated lymphocyte supernatant revealed two peaks of HRF activity in the molecular weight ranges 35,000-50,000 and 3,000-7,000.