Immunocompetent cells of the upper airway: Functions in normal and diseased mucosa

Abstract

Secretory immunity is central in primary defense of the airway mucosa. B cells involved in this local immune system are initially stimulated in mucosa-associated lymphoid tissue, including tonsils and adenoids, and then migrate to secretory effector sites where they become immunoglobulin (Ig)-producing plasma cells. Locally produced Ig consists mainly of J-chain-containing dimers and larger polymers of IgA (pIgA) that are selectively transported through glandular cells by an epithelial receptor called secretory component or pIgR. Secretory antibodies perform surface protection by immune exclusion of soluble antigens as well as infectious agents. IgG can also participate in this primary defense because it reaches secretions by passive diffusion similar to IgE. However, the inflammatory properties of antibodies belonging to the latter two classes explain their involvement in mucosal immunopathology when elimination of penetrating antigens is unsuccessful. T helper (Th) cells activated in this process may by a Th2 profile of cytokines promote persistent inflammation with extravasation and priming of eosinophils. This mechanism appears to occur in the late-phase allergic reaction, perhaps driven mainly by interleukin-4 (IL-4) released from mast cells subjected to IgE-mediated degranulation. Eosinophils are potentially tissue-destructive cells, particularly after priming with IL-5. Cytokines also up-regulate adhesion molecules on vascular endothelium and epithelium, thereby enhancing migration of eosinophils and other leukocytes into the mucosa.(ABSTRACT TRUNCATED AT 250 WORDS)

The surface epithelium of recurrent infected palatine tonsils is rich in γδ T cells

“…It is our impression that the distribution of CD4 þ and CD8 þ T cells is quite distinct, with CD4 þ cells clustering in association with B cells in cryptal areas, while CD8 þ T cells are diffusely distributed and mainly homing to the surface epithelium. The predominance of CD8 þ cells within the epithelium is less striking in the upper airways than in the gut [62]. Halstensen & Brandtzaeg suggested that gut CD8 þ T cells proliferate in lamina propria and thereafter rapidly migrate through fenestration of the basement membrane to the epithelium [63].…”

Increased expression of HLA‐DR and CD86 in nasal epithelial cells in allergic rhinitics: antigen presentation to T cells and up‐regulation by diesel exhaust particles

“…However, epithelial cells may also play other important roles via direct cell-to-cell interaction. A proportion of NEC has been reported to express the major histocompatibility complex (MHC) Class II molecule (HLA-DR) [9,[12][13][14][15]. We therefore hypothesized that NEC may probably play a role in antigen presentation.…”

Phenotypic Distribution of T Cells in Human Nasal Mucosa Differs from That in the Gut

“…T cells present in respiratory and gastrointestinal mucosae are believed to play an important role in the regulation of mucosal immune responses to foreign antigens bombarding the mucosal surfaces (1). The local immune systems in both regions are faced with similar problems of discrimination between harmless environmental antigens that should be ignored and infectious microbial antigens that merit rapid and vigorous immune responses.…”