Soluble and Cellular Markers of T Cell Activation in Patients with Pulmonary Sarcoidosis

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Abstract
We have characterized the activation state of T cells in the bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) from patients with sarcoidosis, to obtain more information about their mechanisms of activation. We analyzed the expression of activation markers (CD25, HLA-DR, Leu-8, and two recently defined markers, CD69 and CD27) on T cells by two-color flow cytometry. We also measured the levels of soluble CD27 and soluble CD25 in nonconcentrated BALF and in serum by ELISA. We found that most T cells in BALF from patients, but not in the peripheral blood, expressed CD69, whereas they did not express CD27. The phenotype (CD69+CD27-) of most BALF T cells and the coexpression of CD69 with HLA-DR and/or VLA-1 indicates that they are in a state of recent and persistent activation. We confirmed previous findings of expression of CD25, HLA-DR, and Leu-8 by T lymphocytes in BALF from patients. We also confirmed increased levels of soluble CD25 in the serum from these patients. The levels of sCD27 and sCD25 in the epithelial lining fluid (ELF) were calculated on the basis of urea in BALF and serum. They were increased in the patients compared with control subjects. In both patients and control subjects, levels in ELF were higher than in the peripheral blood. This indicates shedding of sCD27 (and sCD25) in the lung compartment, which likely contributes to levels in the serum. It is known that in vitro CD27+ cells become CD27- after repeated stimulation and that CD27- cells, after restimulation, do not shed sCD27.(ABSTRACT TRUNCATED AT 250 WORDS)