Evaluation of 3H‐Histamine Incorporation into Human Peripheral Blood Leukocytes

We have examined the use of 3H-histamine for evaluating in vitro basophil responses. Incubation of 3H-histamine for 4 h with basophil-enriched mononuclear fractions containing autologous plasma, resulted in the best incorporation of the label. Even so, less than 3% of the added label was actually recovered and other leukocytes also bound or incorporated 3H-histamine. Labeled mononuclear preparations failed to release 3H-histamine when challenged with zymosan-activated serum or anti-IgE, but endogenous histamine released under the same experimental conditions could be determined fluorometrically. The calcium ionophore, A23187, however, did cause a dose-dependent release of 3H-histamine. We conclude that 3H-histamine is not preferentially incorporated into basophil granules, and that this technique cannot be used for assessing allergen and/or IgE-mediated basophil responses.