CONTENTS OF CD4⁺ AND CD8⁺ EFFECTOR MEMORY CELLS AND PROLIFERATIVE ACTIVITY OF T LYMPHOCYTES IN BRONCHIAL ASTHMA

Abstract

Bronchial asthma is a chronic inflammatory disease of the respiratory tract. T-lymphocytes play a key role in pathogenesis of this allergic disease. The reduction in number of naïve T cells and the accumulation of memory T cells in bronchial asthma are accompanied by dysregulation of T lymphocyte function. In present study, we have investigated the contents of different T lymphocyte subpopulations in peripheral blood as well as in resting and PHA-stimulated cultures, along with their proliferative capacity in patients with bronchial asthma and healthy donors. The study included 10 patients with bronchial asthma (age 45.4±11.8 years). One-half of patients was in remission state, the others having been at the stage of clinical exacerbation. The group of donors was formed by healthy individuals matched by gender and age to the patients. Based on expression of cell surface markers CD45R0, CD62L and CD197 (CCR7), the CD4+ and CD8+T lymphocytes were divided into central (Tcm) and effector memory cells (Tem), naïve T lymphocytes (Tnaïve) and terminally differentiated effector cells (Temra) using flow cytometry technique. The proliferative activity of Tcm, Tem and Tnaïve was evaluated in response to PHA as a functional marker of T cells. We have found that the percentage of peripheral CD4+TemCD62L+ and CD8+TemCD62L+ cells in the patients with asthma exacerbation was significantly reduced, if compared to the donors. Following PHA stimulation, these differences in T cell subsets between the groups of patients and donors were not detectable. We performed a correlation analysis between the memory T cell contents and age of the subjects studied. It was shown that the relative amounts of CD4+ and CD8+ memory cells increased with age in asthmatics, but not in healthy donors. Analysis of mitogen-induced proliferation showed that Tcm and Tnaïve cells proliferated more actively than other subpopulations in both groups. Meanwhile, the proliferative activity of CD4+T lymphocytes and subsets of CD8+Tcm, CD4+Tcm and CD4+Tem62L was higher in the group of asthma patients in remission state than in the patients with exacerbating disease, and healthy donors. The revealed increase in the relative number of memory T cells with age suggests that these cells participate in development of bronchial asthma. Proliferative response of the studied subpopulations, which was comparable to the donor values, suggests a functional maintenance of memory T cells and naïve T lymphocytes in bronchial asthma. The increased proliferation of some T-cell subpopulations in asthmatics in remission suggests an activated state of memory T cells. The observed decrease in the number of CD4+TemCD62L+ and CD8+TemCD62L+ in patients with asthma exacerbation may be, by our opinion, associated with an active inflammatory process in the airways.