Mucosal Immunity Flashcards
What is lung mucosal immunity?
- bacterial metabolites = tolerance
- immune modulation: mucosal tissues share responses w/other mucosal tissues
- coating effect (vaginal birth)
- balance between low/high inflammation microbes=homeostasis
What aspects make the lung a unique microbial niche?
- bidirectional flow of air
- low # of nutrients
GI is one way.
How does the microbiota protect the lung?
colonization early in life protects from inhaled antigens
What region of the lung has the most mucus? The least?
upper airways have more
(trachea and up)
catches what we breath in
What is the mucociliary elevator? Where do the particles go?
goblet cells make mucus that traps microbes –> cilia moves up to GI tract
Which cells provide the movement for the mucociliary elevator?
- goblet cells: mucus to catch microbes
- epithelial: cilia
List the antimicrobial molecules located in the lungs (4)
- lysozyme
- lactoferrin
- LL37 (cathelicidin)
- surfactants (A & D)
What are the most common immune proteins in the lung airway surface interface?
- lysozyme
- lactoferrin
What are surfactants? Which contribute to host defense?
type II epithelium
- lecithins that bind immune cells
- SP-A & SP-D
What are the mechanisms of action for the immune-associated
surfactants?
- Surfactant A (SP-A): ROS, activates MF, opsonization
- Surfactant D (SP-D): opsonizes more microbes, counteracts IL-1 & TNF (anti-inflammation)
What is the mucosal antibody isotype?
What is the most abundant subtype in the lungs?
IgA1
IgA2 in gut
What are the functions and characteristics of IgA?
- Does NOT cause inflammation or fix complement
- joined by J-chain tail-to-tail
What molecule moves IgA to the lumen? How does it work?
Poly-Ig receptor (pIgR) transfers across epithelial surface
How do IgG and IgE reach the airways?
diffusion
List the 6 types of lung epithelial cells
and their role in immune defenses.
- ciliated
- goblet
- neuroendocrine (repair)
- club cells (secrete mucus at bifurcation)
- type II pneumocytes/epithelial (APC action; usually T-reg response)
- M cells (found in FAE)
M cells are only found where?
where there is structured lymphoid tissue (i.e. nasal FAE)
(sometimes epithelium can differentiate into M cell briefly and return)
What does FAE stand for? Where is it located?
- follicular associated epithelium (contains M cells)
- upper airways
How does the cell composition of the FAE differ
from the rest of the epithelium?
- no immune tissues in mucosa
- no goblet cells
- lymphocytes
- APCs
- M cells
this is a microbe pit
What is the Common Mucosal Immune
System? How do mucosal sites across the
body share activated lymphocytes?
induction response in FAE –> spreads to effector sites
(since the lungs don’t have this, they are the EFFECTOR SITE)
What is Waldeyer’s Ring and how does it function in immunity?
- adenoids, tonsils, NALT
- Ag delivered directly here through epithelial cell surfaces (as opposed to lymph)
- Prolific IgA production
Where is the NALT found? Is it in the same place for each individual?
In the nasal passage, underneath FAE
No, it is variable
How is the structure of a MALT similar to a Lymph node? What structures do they share?
they both have MF, B cells and T cells that interact w/Ag
MALT is associated w/M cells and FAE and has the ability to induce microbes into the lamina propria
What is the function of the MALT in activating adaptive immune responses?
ag presentation
Where would an APC go if it were activated in the upper respiratory tract?
In the lower respiratory tract?
- upper airways go to cervical nodes
- lower airways go to mediastinal nodes
