Lecture 16 - Mucosal Immunity Flashcards
Why is mucosal immunity important to a small animal practice
- KC
- coronavirus
- Influenza
- FeLV/FIV
Why is mucosal immunity important to a farm animal practice
- BVD
- BRD (shipping fever)
- mastitis
Why is mucosal immunity important to an equine practice
- strangles
- herpes
- salmonella
Mucosal immunity can be broken into what 6 subdivision
- physical barrier
- clearance mechanisms
- Physiologic adaptations
- chemical defenses
- enzymatic proteins
- antimicrobial peptides
Physical barrier can be broken in what subdivisions
- Mucus - physicochemical
- normal epithelium
- flora
- keratin plug (mammary gland)
Clearance mechanisms can be broken in what subdivisions
- Peristalsis
- Phagocytosis- neutrophils and macrophages
Physiological adaptations can be broken in what subdivisions
- temperature
- pH
- secretions
Chemical defenses can be broken in what subdivisions
- superoxide
- nitric oxide
Enzymatic proteins can be broken in what subdivisions
- lysozyme
- complement cascade proteins
Antimicrobial peptides can be broken in what subdivisions
- iron binding proteins (lactoferrin, transferrin)
- Small cationic hydrophobic peptides
- Inducible or constitutive
- synergy may occur betweem different peptides
What are the 3 main mucosal surfaces
- intestinal
- respiratory
- urogenital
List the parts of the respiratory tract in order of particles that may enter (largest to smallest)
upper respiratory tract (15 um), bronchi (10 um), bronchioles (5 um), alveoli (1 um)
What are the physical barriers and clearance mechanisms in the respiratory tract
- turbinates
- mucociliary apparatus
- alveolar macrophages
What are the physical barriers and clearance mechanisms in the mammary gland
- keratin
- milk
What are the physical barriers and clearance mechanisms in the genitourinary tract
- mucus
- lactic acid
- urine
What are the physical barriers and clearance mechanisms in the GIT
peristalsis
Physiologic adaptation in the gastric barrier
pH
Physiologic adaptation in bile secretions
inactivate some viruses and bacteria
Physiologic adaptation in epithelium
turnover
Physiologic adaptation in mucus
entrapment
Physiologic adaptations/chemical
defenses for microflora
- competition
- by-products
Physiologic adaptations/chemical
defenses for chemical defenses
- super oxide
- nitric oxide
Physiologic adaptations/Enzymes that are protein inhibitors
- lactoferrin
- lysozyme
- interferon
- complement
Physiologic adaptations/Enzymes that are antimicrobial peptides
- small cationic hydrophobic peptides
- inducible or constituitive
- synergy with other peptides
- defensins, cathelicidins, lectins
Where is the site of the common mucosal immune response for the adaptive response
Peyer’s patches
Intestinal mucosal adaptive response
1. Antigen crosses ______
* ____ or other mechanism
2. ______ process and present antigen
3. ____ activation in _______
4. Cells leave inductive tissue via _____
5. Can travel to ______
* Mucosal lymphocytes will home to mucosa due to _________
- intestinal barrier, M-cell
- APCs
- T/B, regional lymphoid tissue
- lymphatics
- distant lymphoid tissue; adhesion molecules, chemokines
What is inductive sites in mucosal adaptive response
where antigen is processed and B/T cells are activated
What are the inductive sites associated with the mucosal adaptive response
- GALT
- BALT/NALT for respiratory (don’t have M cells)
Where is antigen sampling in the inductive site
from lumen not afferent lymph
What are the components of inductive sites
- dome (M cells)
- follicle
- para-follicular region
What are M (microfold) cells responsible for
transcytosis of antigens across gut epithelium and release to APCs at basal surface
2 sites of mucosal adaptive immune response
- inductive sites
- effector sites
What are effector sites
where antibodies and cell-mediated responses are mounted
Where are effector sites
- lamina propria of GIT, respiratory, repro
- secretory glandular tissue
- peyer’s patches; most in diffuse lymphoid nodules
Examples of secretory glandular tissue
- lacrimal
- salivary
- mammary
What can activated B and T cells in effector sites do
relocate and express effector function
What do adhesion molecules and chemokines do to mucosal B and T cells
direct lymphocytes to specific tissues
What are examples of adhesion molecules and chemokines that home B and T cells to epithelial surfaces
- L-selectin
- a4B7 integrin
- CCL25 chemokines
B-cells that originate in ____________ travel to lymphoid follicles for expansion then migrate to ________
- inductive tissue
- lamina propria
What do B cells secrete and which predominates
- IgA, IgG, IgM, IgE
- IgA- 80% of plasma cells in body
What is the secretory product for mammary gland
IgG1, serum derived
IgG1 has selective transfer via what receptor
FcRn
Secretory IgA is a ____ product
dimeric
Where is the majority of IgA produced
epithelial surface
What is IgA complexed with in plasma cells to form dimeric product
J-chain
Where is IgA secreted
at baso-lateral surface of epithelial cells
What does IgA do after binding to poly-Ig receptor
transported to apical surface via endocytic
What happens after IgA is transported to apical surface via endocytic vesicle
poly-Ig receptor is then cleaved and IgA is secreted
What localizes IgA to mucus
residual secretory piece
What does residual secretory piece do
localizes IgA to mucus
The poly Ig receptor complex is resistant to
bacterial proteolysis
IgA excludes pathogens by 3 distinct mechanisms at mucosal surfaces
- in lamina propria can bind pathogens
- within epithelial cells can bind viruses
- within lumen can bind pathogens
What do IgE and IgG serve as
second line of humoral defense
What serves as the second line of humoral defense
IgE and IgG
Why are IgE and IgG the second line of humoral defense
used for pathogens that avoid IgA exclusion
Where are IgE secreting cells found
mainly on body surfaces
What leads to an intensified immune response
mast cell degranulation
What does intensified immune response lead to
increased flow of blood rich in IgG
In the cell mediated response the majority of T cells are
CD8+
CD8+ T cells recirculate continuously between …
epithelilal surfaces and bloodstream
Where are CD8+ T cells found
in lamina propria and beneath/between enterocytes
What are T cells that are within epithelial layer called and what can they do
intra-epithelilar lymphocytes called (IELs); most are yG, can respond directly to antigen
Why are IEL yG CD8-/CD4- T cells in GIT unique
-recognize antigen directly without processing, secrete IFN-y in response
-recognize specialized MHC Ib molecules expressed on stressed cells, binds NKG2D receptor, apoptosis, repair
What infections can affect mucosal surfaces
- feline rhinotracheitis
- bovine rhinotracheitis
- coronavirus
- influenza
Systemic vaccination leads to ___ response
IgG
What leads to IgG response
systemic vaccination
What response is ideal to stimulate
IgA
How can we stimulte IgA response
- apply high levels to surface- consider feed additives
- live attenuated vaccines
What do live attenuated vaccines do
lead to infections at mucosal surface and IgA response
What are 2 live attenuated vaccines
- coronavirus- ineffective in positive cats
- Strangles vaccine