Immunology of Tonsil and Adenoid
Immunologically, tonsils and adenoid are predominently B cell organs. B lymphocytes comprise 60 % of all adenotonsillar lymphocytes, where as T cells constitute the rest 40 %. The immunoreactive lymphoid cells of adenoid and tonsils are found in 4 distinct areas i.e.
1. Reticular cell epithelium
2. Extra follicular areas
3. Mantle zone
4. Germinal centre of follicles
Adenoid and tonsils are involved in inducing secretory immunity. They also play a vital role in regulating secretory immunoglobin production. Their antigen uptake is more or less similar to that of Payer's patches of epithelium in the bowel. Tonsil is infact particularly designed for direct transport of foreign material from exterior to lymphoid cells. The tonsillar crypts play a vital role in this mechanism. These crypts infact not only increases the surface area of the tonsil, it also transports the antigen to the lymphoid follicles.
Human tonsils are immunologically most active between 4 - 10 years of age. Involution of tonsils begin after puberty, resulting in a decrease in the ratio of T:B cells. In patients with tonsillitis and adenoiditis, inflammation of surface epithelium results in shedding of immunologically active cells and decrease in antigenic transport leading on to their subsequent replacement with stratified squamous epithelium. These changes in turn lead to a decrease in the activation of local B cell system, thereby causing an over all decrease in antibody production.
In contrast to recurrent tonsillitis, the changes are less pronounced in adenoid hypertrophy where the immuno regulatory function is still intact. Adenoid and tonsils are activve immunologic organs responsible for the mucosal immunity of the entire aero digestive tract.