<i>In vitro</i> histamine release from basophils of asthmatic and atopic individuals in D2O.

Abstract

Abstract We found that spontaneous histamine release from human basophils in H2O-based buffers is negligible; in D2O-based buffers, however, release is observed with the cells of some donors. Analysis of this phenomenon revealed release from the basophils of 1 of 22 control individuals (5%), 15 of 47 patients with allergic rhinitis (32%), and 14 of 20 asthmatic patients (70%). The difference between both patient groups and controls and between atopics and asthmatics was highly significant. That D2O release was not cytotoxic is suggested by the finding that 37°C was optimal, with inhibition at 4°C or 46°C as well as by EDTA, 2-deoxyglucose, and dibromoacetophenone, an inhibitor of phospholipase A2. The release mechanism was unusual in that dibutyryl cAMP and agonists that cause an increase in cAMP led to no inhibition. No correlation was noted between the total serum IgE level (and thus the number of IgE receptors on the basophil surface) and the magnitude of D2O release. No increase in D2O release was observed in 17 ragweed-sensitive patients through a ragweed season. A unique property of D2O release was the loss of reactivity by preincubating cells at 37°C for 30 min before adding D2O. Non-D2O-reactive cells could be “converted” to D2O-reactive cells by incubation with antigen in the whole blood phase during leukocyte isolation; these cells showed the same loss of releasability at 37°C and an inhibitor profile similar to D2O-responsive cells from ragweed allergic or asthmatic patients. We suggest that D2O-based buffers reveal, in atopic and asthmatic patients, in vivo basophil activation; whether this is due to IgE cross-links, to C split products, or to other stimuli is not yet clear.