Desensitization of human basophils with suboptimal concentrations of agonist. Evidence for reversible and irreversible desensitization.

Leucocytes from allergic donors were preincubated with suboptimal concentrations of ragweed or anti-IgE and then challenged with increasing concentrations of the homologous or heterologous agonist. The initial incubation resulted in desensitization, as judged by a reduced reactivity relative to controls preincubated without agonist but challenged similarly. Both homologous and heterologous desensitization were observed and were dose dependent. Evidence was obtained for both a reversible and irreversible component of desensitization, which was also agonist-concentration related. Reversibility occurred to a similar degree either by incubation of suboptimally desensitized cells with optimal concentrations of agonist or by removal of IgE and resensitization. This could implicate IgE-agonist aggregation on the basophil surface as a mechanism of desensitization. Histamine release from desensitized cells was highly correlated with degranulation, suggesting that individual cells were desensitized in an all-or-none manner.