Immunology Flashcards
Stimulation of the immune system by viruses and bacteria would protect or defect against developing allergies
Protect.
What cell is mostly responsible for allergies?
T-helper2
What might protect against the Th2 phenotype?
Having older siblings
Living on a farm
Frequent helminth infections
What are the steps of the anaphylactic reaction to an allergen? (5)
Allergen recognition Antigen presentation Activation of CD4+ve Th2 cells Th2 interact with B cells Mast cell degranulation
What happens in antigen recognition and presentation in response to an allergen?
Allergen has to gain access to the tissues or a dendritic cell must sample to airway environment. In respiratory viral infections a loss in the epithelial layer can occur.
What are dendritic cells?
APC cells that recognise and engulf non-self and present it to the immune system in conjunction with the MHC II
How are CD4+ Th2 cells activated by dendritic cells?
- The MHCII with antigen is presented to the TCR on the T-cell.
- A co-stimulatory signal is produced from the interaction of CD80/86 on the Dendritic cell with CD28.
How do Th₂ cells then activate B cells in response to an allergen?
The Th2 cell presents the antigen fragment to the B cells and the Th2 cell cytokine IL-4 and IL-13 promote the lass switch to IgE
What is FcℇRI and it’s interaction with IgE?
Expressed only on mast cells as the receptor for IgE, it binds with extremely high affinity.
Actions of histamine?
Opening of capillary bed to increase blood flow to the affected area
Pain/itch
Smooth muscle constriction
Leucocyte recruitment to the area
Consequences of allergen exposure?
Eyes get itchy, red and watery
Nose - sneezing running and itch.
Airways - chest tightness
GI tract - Cramp, Diarrhoea
What lipid mediator is a potent bronchoconstrictor
CysLt, which is a leukotriene.
What anatomical changes cause bronchoconstriction when exposed by an allergen?
Initially contraction of bronchial smooth muscle
After 30mins it is the airway lumen.
What’s the difference in an allergy and asthma?
In an allergy it is the release of mast cell mediators.
What causes a second wave of smooth muscle constriction?
Eosinophils by releasing mediators such as CysLT, eosinophil granules are also toxic to epithelial cells and stimulate mucus production.
What are the histological changes of the asthmatic lung?
Increased mucus production
Thickening of lamina reticularis
Hypertrophy and hyperplasia of the bronchial smooth muscle
Common viruses causing a cold?
Rhinovirus 30-35%, coronavirus 10%, flu virus
Common causes for a sore throat?
Cold viruses cause about 40%
Bacteria cause about 15%
What is RSV?
Respiratory syncytial virus
Can cause bronchiolitis in children.
Antibodies are not very effective
Associated complications of RSV and treatments?
Otitis media, Tracheo-bronchitis with prolonged cough.
Most cases just require hydration and symptomatic relief
Ribavirin to those at sever risk.
Structure of the influenza virus?
RNA virus with a genome consisting of 8 units
Enveloped and consists of three different types.
Complications of influenza virus?
Exacerbation of chronic underlying issues.
Pneumonia
Rye’s syndrome
What are the two types of antigen on the flu viruses envelope?
haemagglutinin
neuraminidase
Difference in influence A/B and then C?
A and B both undergo antigenic shifts (‘mutates’)
