T lymphocytes in allergic rhinitis

Abstract: The role of the T lymphocyte and T cell associated events in the allergic reaction were investigated in the nasal mucosa and in the peripheral blood. Patients with seasonal allergic rhinitis (birch pollen) and healthy controls were subjected to an allergen provocation study during non-pollen season. The subjects were also studied during the natural pollen season.T helper cells have recently been subdivided into two majorsubpopulations according to their cytokine synthesis upon activation. Naive T cells synthesis e.g. IL-2 whilst memory T cells produces e.g. IL-4 and IL-5. These cytokines have been associated to lgE synthesis and eosinophilia, respectively.In peripheral blood, patients with allergic rhinitis have an increased T cell activation even when not exposed to allergen. During the allergen provocation study a further increase in peripheral blood T cell activation occurred. During natural pollen season there is, among allergic patients only, a T helper cell population shifting from naive to memory T cell phenotype in the peripheral blood.A computerized image analysis method was evaluated concerning standardisation of image acquiring and processing as well as sample size. This method was highly reproducible and was used to assess T cell subpopulation stained by immunohistochemistry in nasal biopsies.T memory cell predominates within the nasal mucosa of allergic patients as well as healthy controls. Early during the allergic reaction there is a local T cell activation. Later during the allergic reaction there is an increase of the T cell and the CD45R0+ memory phenotype, in allergic subjects only. Furthermore, allergic patients have an increased expression of the endothelial adhesion molecule VCAM-1 during the allergic reaction.During the allergic reaction, allergic patients have an increased local synthesis of IL-4 and IL-5 as determined by RT-PCR. This may constitute the basis for the increased endothelial VCAM-1 expression and the concomitant homing of memory T helper cells to the nasal mucosa from  the peripheral blood.Topical steroid treatment inhibits local IL-4 synthesis, endothelial VCAM-1 expression and the accumulation ofCD45R0+ memory cells.