Immunology 1 Flashcards
(42 cards)
why do mucosal surfaces require high level of immunity?
they are the primary source of entry of infections
perform critical functions
vulnerable due to fragility and permeability
what are the possible consequences of dysregulated mucosal immunity?
primary immunodeficiency
allergy
coeliac disease
inflammatory bowel disease
what are the 4 functions of mucosal tissue?
gas exchange
food absorption
sensory activities
reproduction
what 2 types of movement can occur through epithelium?
paracellular (between cells through tight junctions)
transcellular (through cell)
Both are passive, but selective
there is a system of mucosal immunity throughout the body, what are the implications of this?
if there is an invasion in a single mucosal site, you can get an immune response in many sites
secondary lymphoid tissue covers most mucosal sites to monitor pathogen entry, true or false?
true
what happens in the lymph nodes during an immune response?
dendritic cells enter lymph node via afferent lymphatic vessel into the paracortical area
T cells enter lymoh node in the blood
If antigen presented by dendritic cell and specific T cell match, T cells become activated and leave to return to site of infection
What are the unique features of the gut mucosal immune system?
organised lymphoid structures unique to mucosal sites
specialised antigen uptake mechanisms
describe the effector mechanisms of the gut mucosal immune system
predominantly activated and memory T cells
natural effector/regulatory T cells also work in the background to dampen down immune response
what is the immunoregulatory environment and what is its importance?
active down regulation of immune response via inhibitory macrophages and tolerizing dendritic cells
prevents inflammatory response to non-harmful substances (hypersensitivity)
prevents chronic inflammation - ie Chrons
what is a peyers patch?
small mass of lymphoid tissue in lamina propria of organized gut tissue
where gut contents (potential antigens) are sampled
where are immune cells found in the lining of the gut?
in the lamina propria
describe the covering of peyers patches
“Dome” of follicle associated epithelium interspaced by M cells (microvilli cells)
what happens inside peyers patches?
antigens can pass through M cells to be sampled by dendritic cells below.
Dendritic cells present antigen to T cells (enter peyers patch from blood vessels, directed by CCR7 and L selectin)
If its a match the T cells move to lymph node (via mesenteric lymphatics) for full activation then come back to the gut in the blood expressing CCR9 and alpha4;Beta7
what do peyers patches look like histologically?
dense purple as they are packed with unactivated lymphocytes
apart from antigens passing through M cells, how else can antigens be sampled?
dendritic cells can extend a process through the endothelial layer and grab antigens from gut lumen
what immune cells exist in the lamina propria?
CD4 T cell Dendritic cell Macrophages Mast cell IgA Plasma cell CD8 T cell
what immune cells exist in the epithelial layer?
Dendritic cells
CD8 T cells
how are activated T cells directed back towards the lamina propria?
via the action of MAdCAM-1
CCR9 on T cell binds to MAdCAM-1 on blood vessel epithelium
Gut epithelial cells chemokines specific for the T cells
if mucosal lymphocytes are activated in one site, why to they migrate back to several areas?
MAdCAM-1 is expressed in many areas
by what methods is passive immunity achieved?
placenta breast milk (IgA)
In what ways are gut antibodies different to circulatory antibodies?
IgA = most abundant (80%)
IgG = least abundant (5%)
IgA = dimeric, joined by J chain
Mostly IgA1
How does dimeric IgA work?
Secreted in lamina propria Binds to poly Ig receptor on endothelial cell Endocytosed into epithelial cell Transcytosed across cell to apical face Released directly into lumen of gut
through which 3 methods can dimeric IgA get rid of antigens?
1) IgA coating the gut lining can bind and neutralize pathogens and toxins
2) IgA can bind and neutralize antigens inside the endosome while passing through the cell
3) IgA can bind to pathogens and toxins in the lamina propria and pass through the cell binded to them
The IgA-antibody complexes are then swept away with the mucus lining the gut
