3. Antibody classes Flashcards
how many IgG subtypes?
4
how many IgA subtypes?
2
what type of molecules are Ab?
immunoglobulins, glycoproteins
5 places you would find Ab
- breast milk
- blood
- saliva
4, tears - plasma
which is the most abundant Ab in plasma?
IgG
which Ab has longest half life?
IgG
which Ab is predominant in secondary response?
IgG
which Ab is used in vaccination?
IgG
which Ig crosses the placenta?
IgG
which disease can be caused by IgG? explain it
Haemolytic disease of newborn
- 1st baby is rhesus +ve and mother is -ve
- Baby Ag cross placenta
- Mother creates Ab
- in second preg - Ab cross placenta and kill baby
Describe IgG structure
4 polypeptide chains ; 2 heavy and 2 light joined by disuphide bonds (3)
2 identical Fab regions (antigen binding) and 1 Fc region (Ab binding to receptor) (2)
which Ab needs to be matched during blood transfusions?
IgG
in the diffferent IgG subclasses- which part of the Ab differs? how does it differ?
Fc region - difference in AA
All IgG subclasses can cross the placenta except?
IgG2
State what each IgG subclass is produced in response to
IgG1 + 3 = T-cell dependent antigens (viral ag)
IgG2 = polysaccharide Ag
IgG4 = extracellular parasites
which IgG subclasses are higher in childhood and which are higher in adulthood?
IgG1 + 3 = children
IgG2 = adult
IgG can be measured to diagnose what disease?
autoimmune hepatitis
IgG can be measured for check serological immunity (after vaccination) - for what 5 diseases?
MMR, Hep B, Varicella (chicken pox)
which is the largest Ab?
IgM
when is IgM produced?
primary response
where is IgM found?
lymph nodes + secretions
does IgM cross the placenta?
no
what does IgM activate?
complement
Describe structure of IgM (4)
- pentamer (5 Ab)
- joined by disulphide bonds and protein J chain
- larger heavy chains
- 10 epitopes - but only 5 bind due to size
give 3 diseases where IgM is raised?
- liver disease
- myeloma
- Waldenstrom’s macroglobinanaemia
give 3 times where IgM is low?
- infancy
- acquired deficiency
- hereditary deficiency
Describe haemolytic blood transfusion reaction
- when someone is not given their blood group in a transfusion
- blood cells attack and cause destruction of incompatible blood
what is mutliple myeloma?
cancer of plasma cells
pathophysiology of mutliple myeloma
- plasma cells produce paraprotein - Abnormal M protein
2. Protein builds up in the blood, urine, bone marrow
SXS of mutliple myeloma
no lump
prescence of paraprotein in blood/urine
why does mutliple myeloma have its name?
it affects multiple places around the body - spine, skill, pelvis, rib cage, long bones
What is waldenstrom’s macroglobinanaemia ?
cancer of plasma cells - high levels of IgM
where is IgA most prevalent?
secretions
function of IgA
protect mucosal surface from infection
most numerous IgA subtype?
IgA1
describe structure of IgA subtypes
IgA1 = monomer
IgA2 = dimer which is held together by disulphide bonds and J chain
has additional secretory protein wrapped around Fc region
where is IgA2 found?
saliva, tears, colostrum (breastmilk), mucus, sweat, glands, gastric fluid
what cells produce IgA2?
epithelial
which surfaces are protected by IgA2?
- resp
- GI
- Genitourinary
what is the most common Ig deficiency?
IgA
what 3 diseases are IgA deficienct people prone to?
- chest infection
- coeliac disease
- pernicious anaemia
Least abundant and shortest half life Ab
IgE
function of IgE
immunity to parasites + helminths
Describe physiology of IgE
- parasite/helminth invades
- IgE attaches to receptors on basophils + mast cells
- causes secretion of proteolytic enzymes, histamine + tryptase to kill pathogen
when IgE binds to mast cells, it can cause Type 1 hypersensitivity. give 3 examples of this
- allergic asthma
- allergic rhinitis
- food allergies
name of syndrome where IgE is high
Job’s syndrome
SXS of Jobs syndrom
- skin, resp + ear abscesses
2. weak immune response
cause of Job’s syndrome
defect of STAT3 gene on chromosome 4
which other Ab can bind to basophils and mast cells?
IgD
where is IgD found?
membrane
what is HIDS?
Hyper IgD syndrome
SXS of HIDS (5)
- skin rashes
- fever
- abdo pain
- vomiting
- sudden onset pyrexia
cause of HIDS
mevalonate kinase gene mutation
in class switch recombination, which region of the Ab changes?
constant
how does CSR occur on a molecular level?
interchromosomal deletion, recombination
In CSR: where does the DNA break?
switch region
In CSR: where does substitution occur?
constant region
In CSR: what causes free ends of DNA to join back together?
NHEJ - non-homologous end joining
