Immunity at Mucosal Surfaces Flashcards
Size of mucosal surfaces in humans
When stretched out and combined, would cover an entire basketball court
Mucosal surfaces as an immune compartment
- More than 90% of all infections start at mucosal site
- Largest immune compartment in the body
- Includes gastrointestinal, genital tract, eyes, ears, glands, etc.
Function of mucosal surface
Distinguish between harmful antigens and food, and environmental antigens and commensals
Mucosal vaccines
- Highly effective as this is the site for so many infections
- Vaccine delivery is an issue
Licensed mucosal vaccines
- Canine: Bordetella
- Feline: calicivirus
- Equine: influenza virus
- Porcine: rotavirus
- Bovine: rotavirus or coronavirus
Respiratory tree
- Gets smaller and smaller
- Trachea to bronchus (main, lobar, segmented) to bronchioles and eventually alveoli
- Alveoli- one layer of cells where all gas exchange takes place
Alveoli and mucous
Mucous is preventing pathogens from reaching alveoli and moving it up and out of lungs
Respiratory epithelium
One layer of epithelial cells only between the environment and the host tissue
- Cilia on surface for mucus transport
- Goblet cells for mucus production
- Lamina propria- tissue under the connective tissue that is full of immune cells
Slight differences throughout the respiratory tree
- Alveoli only have alveolar cells making a very thin layer and there is less organized
Intestinal mucosa
One layer of epithelial cell only between environment and the inside of host
- Vili stick into the lumen of the gut
- Lamina propria full of immune cells (where we find most of the immune cells of the body)
»Immune cells high prevalence due to the fact that this area is where high levels of absorption is occurring and pathogens are trying to enter.
Inductive sites
- Where the immune response is being induced (lymphoid tissues)
- Site of antigen uptake
Effector sites
- Site of immune response
- Where we can find effector lymphocytes. These lymphocytes have seen their specific antigen and after clonal expansion are migrating from lymph nodes to tissue
Ex. Lamina propria and intraepithelial layer of the tissues
Inductive site in the upper respiratory tract
Tonsils
Inductive sites in the gastrointestinal tract
Peyer’s patch
Cells of the inductive sites
- M cells
- Dendritic cells
- Epithelial cells
Cells of the effector sites
- B cells
- T helper cells
- Cytotoxic T cells
- Regulatory T cells
Mechanisms of Antigen uptake at inductive sites
- M cells
- Dendritic cells
- Sneaking in during IgA release at mucosal surfaces when the pinch off occurs. Comes inside with the recycling of the pIgR?
Antigen uptake by M cells (microvilli cells)
M cells are highly specialized epithelial cells that form a “trap” while sitting on top of the Peyer’s patch in the epithelial layer
- They have shorter glycocalyx on their surface and thus particles fall into trap and allow cells to take them up
- They also have pockets on their basal side which immune cells can get access to the antigen
Antigen uptake by dendritic cells
- Dendritic cells can hang out their dendrites into the lumen and fish for antigens
- They will then present the antigen to the T cells for activation of immune response, and then the T helper cells activate the B cells
- Occurs at all mucosal surfaces
Mucosal surfaces of Oral cavity and vagina
- Also has dendritic cells uptaking antigens
- They need mechanical protection so have more layers of epithelial (dying or dead cells). Dendrites are able to migrate up and sit in the dead cells
Steps of antigen uptake at inductive sites
- Antigen taken up at inductive sites
- Lymphocytes are induced when presented antigens
- Activated lymphocytes leave the inductive sites and migrate to the effector sites where they do their job. (Remember there are different effector cell populations in these tissues. Ex. B cells/plasma cells producing IgA or T helper cells releasing cytokines)