Immunological studies of adenoids in children : relation to atopy

Abstract

The nasopharyngeal tonsil or adenoids is in constant interaction with our environment with every breath we take. This organ, rich in B cells, contains all the immunocompetent cells necessary for an interaction with T cells, exerted through secretion of cytokines and resulting in the production of immunoglobulins and the formation of memory cells. As part of Waldeyer's pharyngeal ring and of the mucosa-associated lymphoid tissue it plays an important role as a source of B cells for other parts of the upper respiratory tract. Adenoids act as a site for the induction of local and distant antibody responses in the defense against airway pathogens. The precise role and function of adenoids in the interactions between its own lymphoid cells and inhaled allergens is, however, poorly understood. Very little is known about the relationship between adenoid tissue and atopic diseases, and the local source of immunoglobulin (Ig)E- producing cells in the respiratory tract has been debated and is largely unknown.

AIMS: The present work was performed with the ambition to increase our knowledge about the immunological functions of adenoid tissue in children, and put this in relation to atopy by investigating: - if the presence of atopy influences the microenviroment of adenoids with respect to cellular and other immunological findings; - if there are age-related differences in lymphocyte subpopulations in adenoids that support the hypothesis that this organ is involved in the development of immunological memory; - if differences observed in the context of atopy are in agreement with current knowledge regarding the immunology of atopic reactions; - if there is evidence of the adenoid tissue being involved in the development of IgE-mediated reactions, with IgE production taking place in adenoids.

MATERIALS AND METHODS: Adenoids were surgically removed (adenoidectomy) from atopic and non-atopic children with adenoidal hyperplasia or otitis media with effusion. Children were classified as atopic if they had a positive PhadiatopR. OBS Flow cytometry and immunohistochemical methods were used to investigate lymphoid cell populations and subpopulations, transcripts of the cytokines IL-4 and IFN-gamma, epsilon germ line (epsilonGL) transcripts, secretion of the cytokines IL-2, IL-4 and IFN-gamma after non-specific stimulation, presence of IgE+ cells and IgE+ plasma cells. Peripheral blood lymphoid cell populations and subpopulations were also examined and related to the same populations in adenoids.

RESULTS AND CONCLUSIONS: In all the studies performed, cellular and other immunological findings indicate a relationship between adenoid tissue and atopy. An increased occurrence of IgE+ cells and IgE+ plasma cells was found in adenoids of atopic compared to non- atopic children. epsilonGL transcripts were found to be dependent on IL-4 mRNA expression and serum IgE levels. Stimulation of adenoid cell cultures from atopic children resulted in a greater increase in B cells, increased activation of T cells and enhanced production of IL-4 but not IFN- gamma, compared to non-atopic children.

The observation that memory T cell subsets in adenoids and blood are related to age indicates a role of adenoid tissue in the development of immunological memory. Besides linking atopy to the immunological function of adenoids, our results support the hypothesis that the adenoid tissue is involved in the development of IgE-mediated reactions and indicate that IgE production takes place locally in adenoids.