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Comparison of mononuclear cell and B-lymphoblastoid histamine-releasing factor and their distinction from an
M Haak-Frendscho1, M Sarfati, G Delespesse
1Department of Medicine, State University of New York, Stony Brook.
We have characterized the histamine-releasing factors (HRF) from a B-lymphoblastoid cell line (RPMI 8866), compared it to mononuclear cell-derived HRF, and distinguished these from the IgE-binding factor produced by RPMI 8866. The B-cell-derived HRF fractionates at molecular weights of 90,000, 70,000, and 12-15,000 while mononuclear cell HRF has a major component at 24-26,000. The isoelectric points for B-cell HRF are 6.2-6.3 and 6.6-6.8 in contrast to 6.9 and 7.3 for mononuclear cell-derived HRF. The kinetics of histamine release by either HRF was the same, with half-maximal release in 5-10 min, unlike the rapid release caused by anti-IgE. Since HRF has been reported to be an IgE-binding factor, we screened column fractions for the IgE-binding factor secreted by RPMI 8866; this is known to be a shed low affinity IgE receptor. The chromatographic pattern and isoelectric point of this IgE-binding factor does not correspond to HRF; the purified IgE-binding factor had no significant histamine releasing activity on human basophils, and neither source of HRF was reactive in a radioimmunoassay to the IgE-binding factor. Our data suggest that HRF is quite heterogeneous and varies in physiochemical properties depending upon the cell source. The molecular relatedness (or nonrelatedness) of those HRFs is unclear; however, our data indicate that although HRF or fractions therefrom may bind to IgE as has been reported, it is unrelated to the low affinity IgE receptor.
We have characterized the histamine-releasing factors (HRF) from a B-lymphoblastoid cell line (RPMI 8866), compared it to mononuclear cell-derived HRF, and distinguished these from the IgE-binding factor produced by RPMI 8866. The B-cell-derived HRF fractionates at molecular weights of 90,000, 70,000, and 12-15,000 while mononuclear cell HRF has a major component at 24-26,000. The isoelectric points for B-cell HRF are 6.2-6.3 and 6.6-6.8 in contrast to 6.9 and 7.3 for mononuclear cell-derived HRF. The kinetics of histamine release by either HRF was the same, with half-maximal release in 5-10 min, unlike the rapid release caused by anti-IgE. Since HRF has been reported to be an IgE-binding factor, we screened column fractions for the IgE-binding factor secreted by RPMI 8866; this is known to be a shed low affinity IgE receptor. The chromatographic pattern and isoelectric point of this IgE-binding factor does not correspond to HRF; the purified IgE-binding factor had no significant histamine releasing activity on human basophils, and neither source of HRF was reactive in a radioimmunoassay to the IgE-binding factor. Our data suggest that HRF is quite heterogeneous and varies in physiochemical properties depending upon the cell source. The molecular relatedness (or nonrelatedness) of those HRFs is unclear; however, our data indicate that although HRF or fractions therefrom may bind to IgE as has been reported, it is unrelated to the low affinity IgE receptor.