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

We have examined the use of 3 H‐histamine for evaluating in vitro basophil responses. Incubation of 3 H‐histainine 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 3 H‐histamine. Labeled mononuclear preparations failed to release 3 H‐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 ionopbore, A23187, however, did cause a dose‐dependent release of 3 H‐histamine. We conclude that 3 H‐histamine is not preferentially incorporated into basophil granules, and that this technique cannot be used for assessing allergen and/or IgE‐mediated basophil responses.