Immunology of tonsils and adenoids: everything the ENT surgeon needs to know.

The lymphoid tissue of Waldeyer's ring, and particularly the nasopharyngeal tonsil (adenoids), appears to be functionally comparable to nasal-associated lymphoid tissue in rodents. Antigen-stimulated lymphoid follicles give rise to: (a) clonal B-cell expansion; (b) B-cell receptor affinity maturation; (c) positive selection of B cells according to receptor affinity for antigen; (d) differentiation to B memory cells and plasma cells; and (e) variable induction of the joining (J)-chain gene. B-cell differentiation is also important to promote downstream isotype switching of the immunoglobulin (Ig) heavy chain constant genes. For tonsillar B cells, this process gives mainly rise to IgG and IgA plasma cells, partially associated with J-chain expression. Because the J chain is a key peptide in the polymer structure of secretory IgA, tonsils and adenoids may provide B cells for mucosal effector sites. Thus, several observations suggest that these lymphoid organs generate polymeric IgA (pIgA)-expressing B cells that migrate to the upper airway mucosa, lacrimal glands and salivary glands. Accordingly, the nasal route of vaccination induces secretory IgA-dependent regional mucosal immunity and will also enhance systemic immunity. Although the pIgA-producing capacity of tonsillar B cells is considerably decreased in children with recurrent tonsillitis, a conservative attitude towards adenotonsillectomy appears immunologically desirable, particularly in the young age group.