T lymphocytes that infiltrate nasal polyps have a specialized phenotype and produce a mixed T-H1/T-H2 pattern of cytokines

Background: Nasal polyps (NPs) are inflammatory reactions in the nasal muco se the etiology and pathogenesis of which remains unknown. Objective: The purpose of this study was to study in detail the phenotype a nd function of T lymphocytes infiltrating NPs by analyzing the expression o f surface markers and cytokine secretion. Methods: NP tissue samples and peripheral blood were obtained from 18 patie nts. Mononuclear cells were purified from these samples, and their phenotyp e was investigated by triple-color immunofluorescence and flow cytometric a nalysis. Cytokine production was determined in cultures by using an ELISA t echnique. Results: NP lymphoid cells mainly consisted of T Lymphocytes. These T lymph ocytes showed a CD45RO+CD45RA- phenotype and expressed pan-T cell molecules ; the CD8+ subset was predominant. NP T cells showed a Lower density of CD2 8, CD3, and TCR-alpha beta compared with T cells from peripheral blood. NP T lymphocytes expressed the activation markers DR and CD69 and exhibited th e adhesion molecule profile CD54+, CD62L-, and CD103+ CD49d(low). Virtually all NP T cells bore CD95 (FAS), but they did not undergo apoptosis, either spontaneously or induced by CD95 cross-linking with the mAb CH11, The patt ern of cytokines secreted by NP T lymphocytes was characterized by the spon taneous and simultaneous production of IFN-gamma and IL-5, Neither IL-2 nor IL-4 were detectable in nonstimulated cultures. Conclusion: This study defines the T lymphocytes that infiltrate NPs as mem ory T cells in an activated status, with homing properties related to the m ucosal immune system, They are resistant to anti-CD95-mediated apoptosis an d produced a mixed T-H1/T-H2 cytokine pattern as defined by the simultaneou s production of IFN-gamma and IL-5.