Allergy 199S: 5.1 233-240 Printed in UK ~ all rights reserved Copyright ® Munksgaard 199S ALLERGY ISSN 0105-4538 Systemic T-cell unresponsiveness during rush bee-venom immunotherapy Segura JA, Assenmacher M. Irsch J, Hunzelmann N, Radbruch A. Systemic T-cell unresponsiveness during rush bee-venom immunotherapy. AUergy 1998: 53: 233-240. © Munksgaard 1998. By rush bee-venom immunotherapy, subjects reacting allergically to the venom can be effectively anergized, although the mechanism of action is not known. Here we analyzed the systemic effects of rush desensitization on the T cells of allergic patients. In most patients, we found reduced frequencies of T cells recalled to express CD69 and the cytokines interleukin (IL)-4 and interferon-gamma (IFN-y) after stimulation of peripheral blood mononuclear cells with phorbol 12-myristate 13-acetate (PMA) and ionomycin, as compared with normal donors. These frequencies are progressively reduced during immunotherapy. The frequency of cells expressing IL-2 does not change. A few patients show a different response to immunotherapy: frequencies of cells expressing CD69, IL-4, or IFN-ydo not change, and remain similar to those of normal donors. However, the frequency of cells able to express IL-2 is increased. The analysis of cytokine expression in CD45RO* vs CD45RO' T-cell populations revealed differences between normal and allergic donors. In allergic patients, higher frequencies of IL-4- and IFN-y-expressing cells among the CD45RO^ subpopulation were found than in normal donors. This situation is not modified by immunotherapy. The results reveal a certain degree of heterogeneity in the response of allergic patients to bee-venom rush immunotherapy; however, all are clearly differentiated from normal controls as judged by cytokine expression of CD45RO T cells. In most allergic patients, a considerable percentage of TTi cells become unresponsive to mitogenic stimulation, and may be responsible for the desensitization itself J, A. Segura\ M. Asseninacher\ J, lrsch\ N, Hunzelmann^ A. Radbruch^ 'Institute for Genetics and ^Department of Dermatology, University of Cologne, Cologne, Germany Key words: bee venom; CD45R0; cytokine stainings; rush desensitization. Juan A. Segura Departamento de Bioquimica y Biologia Molecular Facultad de Ciencias Universidad de Malaga 29071 Malaga Spain Accepted for publication 29 September 1997 Allergic hypersensitivity of type I for bee venotn has been described in about 3% of the North American population (1) and may lead to severe, life-threatening anaphylactic reactions. Venom immunotherapy (VIT) has been shown to be very effective in preventing subsequent anaphylaxis in sensitive subjects, reaching a grade of protection of about 95% in studies of occasional or intentional re-sting events (2, 3). The time needed to reach the maintenance dose of about 100 (xg of venom varies from 1 to 5 days in rush VIT to several months in classical VIT, and monthly injections of the main- tenance dose for a period of 3-5 years are required to maintain the protection (4), Skin tests remain positive after this period in about 80% of the subjects (5, 6). In spite of the effectiveness of this therapy, little is known about the cellular and molecular mechanisms leading to desensitization. Reports claiming that increased concentrations of specific IgG would provide valuable information on desensitization (7) have been questioned (8), Recently, it has been claimed for immunotherapy (IT) of house-dust-mite (9,10) and bee-venom (11, 12) allergy that antigen-specific T cells are induced to change from expression of the IgE-inducing cytokine interleukin (lL)-4 to expression of inter- feron-gamma (IFN-y), which would inhibit de novo class switching to IgE (13, 14). However, this fact alone does not explain desensitization after VIT, since in the course of rush bee-venom IT, titers of specific IgG and IgE do not vary significantly (15), and high titers of IgE are found even after 3 years of IT (16). Early studies during IT of poUinosis have shown diminished proliferation and production of IFN-y and IL-2 by mononuclear cells upon stimu- lation with the specific allergen (17). But also systemic effects of IT have been described, such as decreased proliferation of CD4* lymphocytes to stimulation with phytohemagglutinin (PHA) during classic hyposensitization of asthmatic children (18). 233