Immunology 2 Flashcards
What is a hapten?
An antigen that needs covalent linkage to a carrier to stimulate an immune response eg penicillin
What is a superantigen?
Bind Vbeta chain of the TCR, bypassing the need for MHC to present the antigen–>large number polyclonal T lymphocytes activated
How does adrenaline work?
Act on beta and alpha receptors to cause vasoconstriction and bronchodilation
Downregulate histamine and tryptase release
MOA sodium chromoglycate
stabilise mast cell
prevent degranulation by blocking calcium influx
What has to be done before skin prick testing?
hold antihistamines 4-7 days
RAST can be done on antihistamines
Of T reg cells, IL-10 does what?
Promote IgG4
Of T reg cells, TGF beta does what?
promotes IgA
What are the three sets of things that bind between APC and T cell?
TCR binds to MHC on APC
CD40L on T cell binds CD40 on APC
CD28 on T cell binds B7 AKA CD80/86 on APC
Note CTLA4 on T cell can also bind CD80/86
MHC1 made up of what molecules?
3 alpha chains
and
beta 2 microglobulin
MHC2 made up of what molecules?
2 alpha
2 beta
Which cells express MCH class 2?
Macrophages dendritic cells B lymphocytes Thymic epithelia Activated T cells
The most common autoimmune disease?
Coeliac then Graves
What does GAD actually do?
Involved in glutamate metabolism
Increase age of onset of type 1 DM….
reducing incidence of multiple antibodies being positive
Later onset DM- more GAD, less anti insulin
ie LADA often only GAD positive with intermediate risk HLA
Breast feeding does what to celiac risk?
Lowers
Too much early gluten increases risk
Chronic atrophic gastritis- antral vs corpus
antral gastritis- H pylori
Corpus gastritis- autoimmune
What is thought to be a biomarker of corpus atrophy after you have pernicious anaemia?
Anti gastrin Ab
Which DM1 ab is most sens and spec?
anti GAD
Mechanism of hyponatraemia in secondary or tertiary adrenal insufficiency?
ACTH concentration low or normal
Plasma renin and aldosterone unaffeted, though if long standing can sometimes getmineralocort def
Serum Na often reduced because of reduced inhibition of ADH secretion by no cortisol
Association between rotavirus and celiac disease?
Yes, often precedes
Briefly, what is IPEX?
monogenic FOXP3 geen mutation
Over half have DM1
also enteropathy
X linked
Crohn’s technically not an autoimmune disease, more of an/….
autoinflammatory disease!
INNATE not adaptive immune damage
NOD2 mutation linked to aberrant innate immune response
BASILIXIMAB does what?
IL-2 blocker
Lipopolysaccharides expressed on what cells?
Example of a PAMP- pathogen assoc molecular protein
Seen on gram negative bugs
Lipoteichoic acids expressed on what cells?
Gram positives, example of a PAMP.
What are PRRs?
Pattern recognition receptors- recognise PAMPs
- TLR recognise bacterial cell wall lipid outside cell
- NOD LR recognise bacterial cell wall lipid inside cell
- RIG like receptors recognise viral RNA in cell
Triggering activates cell
What are toll like receptors?
cell surface proteins responsible for host defense. When in contact with microbial peptide, acts via NFkB pathway to upregulate antibicrobial peptides- CK, costim molecules.
Responsible for shock in gram neg sepsis when LPS binds LTR4
What is MBL?
used to be called the universal Ab
an acute phase reactant that is structurally and functionally similar to C1q
Cleaves C4 and C2 for MBL complement pathway
Also an opsonin
Which are the only cells in the body not to express MHC I?
neuronal cells
RBCS- not attacked because lack activating receptor
What is the significance of CCR5 delta 32 in HIV?
This is the molecule tht R5 strains of HIV virus use for entry
Heterozygote- slowed disease progression
Homozygote- resistant to infection
R5 strains infect macrophages and T cells
X4 strains infect T cells only
What is a normal K:l ratio ?
2:1
How do the different Igs differ?
Different appearance of the hinge regions (length) between the Fab and Fc of the Ig
Fc gamma receptors are found where?
On phagocytic cells
Hence IgG is the most important opsoniser.
Which Ig can get to fetus?
IgG
What is the role of FcRn?
This is the neonatal Fc receptor
gut of infant lining cells have these receptors- take up igs but do not degrade! Release into the blood instead!
In adults contributes to the long half life of IgGs
What does IgA look like?
monomer in serum
dimer in secretions
IgM described as…
Low affinity, high avidity
On subsequent Ag exposure, SAME IgM response, faster/better IgG response
Which Ab help with ADCC?
A
G
E
Which Ab fix complement?
A and G
When you look for clonality, what are you looking for?
The exact VJD rearrangement
Rearrangement only occurs in B cells, not somatic cells
