Week 4- Hypersensitivity Flashcards
What are antibody classes know as? How do they differ?
Isotypes, they have different binding capacities and engage with the immune system in different ways
How are T cells activated?
By encountering a specific antigen
What do effector CD4+ T cells do?
Activate B cells, macrophages
What do effector CD8+ T cells do?
Kill infected target cells and activate B cells
What is type I hypersensitivity?
Allergic reaction where antibodies are produced against common multivalents (antigens that have multiple sites for antibody attachment)
What antibodies mediate type I hypersensitivity?
IgE
Describe the pathway of a type I hypersensitivity reaction
- B cell helper follicular CD4 T cells and type 2 helper CD4 T cells produce type 2 cytokines IL3 and IL4
- These encourage B cells to produce antigen specific IgE
- IgE binds to mast cells and basophils via Fc epsilon receptor
- Cross linking and degranulation of basophils/mast cells results in the release of histamine
- Results in Th2 differentiation
What are the 3 phases of type I hypersensitivity reactions and what are their time frames?
- Early phase- mast cells produce small molecules (few mins)
- Later phase- Recruitment of neutrophils (few hrs)
- Third phase- recruitment of eosinophils and Th2 cells (3/4 days)
What happens in type II hypersensitivity reactions?
Destruction of cells by IgG or IgM antibodies binding to antigens on the cell surface
What are some examples of type II hypersensitivity reactions?
Haemolytic disease
Graves’ disease
Mismatched blood transfusion
What are the 3 methods by which antibodies can cause disease? Describe them
- Anti receptor activity
- Antibody dependent cell mediated cytotoxicity- when antibody antigen complexes cause lysis
- Activation of a complement cascade- antibody is recognized by complement components which leads to the formation of a membrane attack complex (MAC) causing cell death due to lack of integrity
What is type III hypersensitivity?
When antibody antigen complexes aren’t removed and deposited in blood vessels, causing inflammation and tissue damage
What is type III hypersensitivity in the blood vessels called?
Vascularitis
What is type III hypersensitivity in the kidneys called?
Glomerulonephritis
What is type III hypersensitivity in the joints called?
Arthritis