Decreased expression of high affinity interleukin 2 receptors after hyposensitization to house dust

The lymphoproliferative response to allergen usually decreases after long-term hyposensitization (immunotherapy). In order to delineate the working mechanism of this kind of treatment, expression of interleukin 2 receptors (IL-2 R) on house dust and phytohemagglutinin-activated lymphocytes was compared in 15 normals, 18 newly diagnosed and 28 hyposensitized asthmatic children. Interleukin 2 receptors were analyzed by fluorescent-activated cell sorter (FACS), uptake of 125I-labelled anti-human IL-2R monoclonal antibody (anti-Tac), and proliferative response to recombinant IL-2 (rIL-2). The results showed that there was no difference in the expression of IL-2R among three studied groups, if IL-2R were detected by anti-Tac. When compared to the other two groups, house dust-activated lymphoblasts from new patients proliferated vigorously in the presence of very low rIL-2 (0.02 to 1.0 nM), suggesting the presence of much higher numbers of high affinity IL-2R. Decreased high affinity IL-2R may partly explain the diminished lymphoproliferation to allergen after long-term hyposensitization.