Background: Nasal polyps (NPs) are inflammatory reactions in the nasal mucosa the etiology and pathogenesis of which remains unknown.
Objective: The purpose of this study was to study in detail the phenotype and function of T lymphocytes infiltrating NPs by analyzing the expression of surface markers and cytokine secretion.
Methods: NP tissue samples and peripheral blood were obtained from 18 patients. Mononuclear cells were purified from these samples, and their phenotype was investigated by triple-color immunofluorescence and flow cytometric analysis. Cytokine production was determined in cultures by using an ELISA technique.
Results: NP lymphoid cells mainly consisted of T lymphocytes. These T lymphocytes showed a CD45RO+CD45RA- phenotype and expressed pan-T cell molecules; the CD8+ subset was predominant. NP T cells showed a lower density of CD28, CD3, and TCR-alphabeta compared with T cells from peripheral blood. NP T lymphocytes expressed the activation markers DR and CD69 and exhibited the adhesion molecule profile CD54+, CD62L-, and CD103+ CD49dlow. 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 pattern of cytokines secreted by NP T lymphocytes was characterized by the spontaneous 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 memory T cells in an activated status, with homing properties related to the mucosal immune system. They are resistant to anti-CD95-mediated apoptosis and produced a mixed TH1 /TH2 cytokine pattern as defined by the simultaneous production of IFN-gamma and IL-5.