A study of the expression of early and late activation markers on the surface of regulatory subsets of human peripheral blood T lymphocytes revealed marked differences between patients with bronchopulmonary pathology and healthy donors in the dynamics of CD25, CD71, and HLA-DR expression. The results are of significance for the evaluation of both the activation state of the cell and its functional potential in the realization of the immune response. Key Words: activation markers; dynamics; CD4+ and CDS+ lymphocytesOne of the features distinguishing activated T lymphocytes from resting T cells is the appearance of various membrane glycoprotein markers that are synthesized de novo in the course of cell activation. Some of the markers, such as receptors of insulin, transferrin (CD71), mterleukin-2 (CD25), CD69, 4F2, and EA-1, appear at the early stages preceding DNA synthesis, while other antigens, including HLA-DR, T10, Tal, VIA1, and TLiSA1, appear later [3,8,9].The content of activated lymphocytes in human peripheral blood has been studied in depth. Earlier we showed a significant increase in the number of activated lymphocytes belonging to the regulatory subsets (CD4, CDS) in patients with infectious-atopic bronchial asthma and tuberculosis as compared to healthy donors [1,2]. However the potential of such lyrnphocytes to be activated in vitro under conditions of a functional load, such as an antigen or mitogen, remains poorly understood. The goal of the present work was to study the dynamics of the early (CD25, CD71) and late (HLA-DR) activation markers on the surface of CD4+ and CD8+ cells using the model of phytohemagglutinin (PHA)-induced lymphocyte proliferation. MATERIALS AND METHODSMononuclear ceils (MNC) of human peripheral venous blood were tested. Blood was taken aseptically from the ulnar vein, in the morning, on an empty stomach. The control group consisted of 51 clinically healthy donors, 32 men and 19 women, aged 17 to 30 years. The group of patients included cases of infectious-atopic asthma at the stage of exacerbation and cases of primarily diagnosed tuberculosis. Eighteen patients with bronchial asthma (7 men and 11 women) aged 25 to 55 years were examined. The patients were under hospital treatment at the Institute of Immunology, Russian Ministry of Public Health. Sensitization to streptococcal and staphylococcal antigens was noted in the anamnesis. We also examined 35 patients with