PERIPHERAL-BLOOD MANIFESTATIONS OF T-H2 LYMPHOCYTE-ACTIVATION IN STABLE ATOPIC ASTHMA AND DURING EXERCISE-INDUCED BRONCHOSPASM

Background: Recently, T-H2 lymphocyte activation has been shown to pla y a key role in initiating and propagating the inflammatory response i n asthmatic airways. This is manifest through increased numbers of ''a ctivated'' CD25-(IL-2R)-bearing T-helper cells and can be seen through the IL-5 driven recruitment of eosinophils and IL-4-mediated B-cell e xpression of CD23 (low affinity IgE receptor) and ultimately IgE produ ction. Objective: To gain a better understanding of the role of immune cells in asthma by describing the peripheral blood immune cell phenot ypes in mild atopic asthma. Methods: We enrolled 13 patients with mild atopic asthma and a group of seven nonatopic, nonasthmatic controls. Objective measures of lung function were obtained. The peripheral bloo d was analyzed by flow cytometry for specific cellular markers at rest and during the development of exercise induced bronchospasm. Results: At rest the number of CD23-bearing B cells (169/mL versus 117/mL; P = .05) and the number of CD25-bearing T cells (355/mL versus 237/mL; P = .03) were increased in the asthma group. There was a linear relation ship between these two lymphocyte subsets and the maximum voluntary ve ntilation at rest (r = 0.56, P = .01 and r = 0.57, P = .01). With the development of exercise-induced bronchospasm there was a significantly greater increase in CD23-positive B cells (96.7/mL versus 59.7/mL; P = .05) and CD25-positive T cells (111.8/mL versus 45.1; P = .01) in th e asthma group. Conclusions: These data indicate that T-H2 lymphocyte activation is manifested by increased numbers of CD23-bearing B cells and CD25-bearing T cells in the peripheral blood of patients with stab le mild atopic asthma. Further, these immune cell subsets correlate wi th markers of resting lung function and increase in the peripheral blo od early after the development of exercise-induced bronchospasm.