Effects of in vivo administration of interleukin-2 (IL-2) and IL-4, alone and in combination, on ex vivo human basophil histamine release

Human basophils possess receptors for interleukin-2 (IL-2) and IL-4. The effect of 3 days of intravenous administration of IL-2 and/or IL-4 on basophil histamine release was examined in three groups of patients receiving IL-2, IL-4, or the combination of agents as part of a protocol to treat malignant melanoma or renal cell carcinoma. Because all patients received ranitidine for control of side effects, a control group of patients receiving ranitidine for Zollinger-Ellison's syndrome was also studied. IL-4 significantly inhibited IgE-mediated histamine release, while there was a trend for enhancement of IgE-mediated histamine release by IL-2. Administration of the combination of IL-2 and IL-4 did not alter IgE-mediated basophil histamine release. Both IL- 2 and IL-4, alone and in combination, enhanced basophil histamine release induced by histamine releasing factors in human nasal washings. The effect of IL-2 alone was significantly greater than that of IL-4 alone or the combination of IL-2 plus IL-4. Taken together, the data suggest that when coadministered, IL-4 may inhibit the effects of IL-2 on basophils. Neither cytokine exerted any effect on basophil histamine release induced by the calcium ionophore A23187, nor did ranitidine cause any effects on histamine release induced by any of the stimulants. Thus, human basophil reactivity can be affected by IL-2 and by IL-4. The role that these two cytokines play in basophil function in vivo is likely to be complex.