-
Describe the organization of lymphoid tissues associated with the respiratory track
- BALT (Bronchus Associated Lymphoid Tissue) is part of a larger system of lymphoid tissue associated w/ mucosal membranes (MALT)
- Both T and B cells are located here and it's main response is IgA antibody
-
Describe the mechanism responsible for preferential recirculation of lymphocytes to mucosal sites
-
What are the innate host defense mechanisms that are involved in protecting the respiratory track from pathogens?
- Anatomical barriers
- Cilia and mucus
- Cells and molecules
-
What are the adaptive host defense mechanisms that are involved in protecting the respiratory track from pathogens?
- B cells - secretory IgA
- T cells
-
What is granuloma?
- Organized collection of macrophages
- Macrophages fuse together to form multi-nuclear Langerhans giant cells
- May contain lymphocytes (T and B), neutrophils, dendritic cells, fibroblasts, and collagen
-
Describe the immunologic mechanisms involved in granuloma formation
- Analogous to a Type IV Hypersensitivity reaction
- Alveolar macrophages phagocytize pathogen (M. tuberculosis)
- Macrophages secrete cytokines and chemokines
- IL-1, IL-6, TNF-a
- IL-10, IL-12, IL-18
- Antigen processed and presented to CD4+ and CD8+ T lymphocytes
- T lymphocytes (primarily CD4+) are activated and secrete cytokines (IFN-y, IL-2)
- TH1 cells preferentially stimulated
- Inflammation initiated resulting in formation of granuloma and walling off of pathogen
-
-
What is serum IgA?
- Monomeric IgA
- Types: IgA1 and IgA2
-
How is secretory IgA produced?
- Antigen is transported across the epithelium by M cells to the lamina propria where they are processed by resident macrophages (APC)
- The processed antigen is presented by class II HLA bearing APC to CD4 T cells
- The T cells activate B cells to produce IgA dimers which are secreted and bind to a receptor, the polymeric immunoglobulin receptor, on the epithelium cell
- The complex of receptor and IgA crosses the epithelium and is exocytosed into the gut lumen
- A portion of the receptor remains w/ the IgA dimer forming the secretory component (SC)
- The complex of IgA dimer, J chain, and SC comprises secretory IgA
-
Identify J chain and secretory component
J chain -
|
|
