Immunodeficiency (core immunology) Flashcards
What are the mechanisms of the innate immune system?
1) Barrier and chemical mechanisms
2) PRR (on macrophages activate adapt immune system recognising pathogen, then cells secretes cytokines)
4) Complement (Opsonisation and cell lysis)
3) Cellular (Phagocytes and NK cells)
What are the mechanisms of the adaptive immune system?
Helper T cells recognise antigen-MHC 2 complex on APC. Secrete cytokines which attract Macrophages and activate B cells.
B cells secrete antibodies. proliferate and produce memory cells.
Cytotoxic T cells induce apoptosis of infected cell
Describe the key features of the complement cascade?
Classical Pathway:
Activated by antibody-antigen binding.
lectin pathway:
MBL binds to sugar on bacteria this activates.
Alternative pathway:
activation of C3 by direct exposure to bacteria cell wall and endotoxin.
C3b - opsonisation
C3a and C5a - anaphylaxis
C5,6,7,8,9 - membrane attack complex
How does the binding of antibodies to antigens inactivate the antigen?
(3 mechanisms)
1) Neutralization
(binding blocks the viral binding site / coates bacteria)
2) Binding caused the microbes to stick together.
3) Binding causes the precipitation of dissolved antigens.
***All of the above enchances phagocytosis
How does a cytotoxic T cell destroy infected cells?
1) Killer T cells binds to infected cell
2) Perforin released by the T cell makes holes in the infected cell’s membrane and enzyme enters.
3) The enzyne that promotes apoptosis is also secreted
4) Infected cell destroyed
What are the causes of immunodeficiency?
Primary - genetic defects in individual components of the immune system.
Secondary - to effects of external factors.
What are the causes of secondary immunodeficiencies?
- stress
- surgery
- malnutrition
- cancer
- immunosuppressives
- AIDS
- other inf eg. measles.
What is chronic granulomatous disease?
genetically heterogeneous immunodeficiency disorder resulting from an inability of phagocytes to kill bacteria and fungi that they have ingested.
What are the signs and symptoms of chronic granulomatous disease?
- osteomyelitis
- pneumonia
- swollen lymph nodes
- ginigivitis
- non malignant granuloma
- Inflammatory bowel disease
What is X linked agammaglobulinaemia?
X linked agammaglobulinaemia also known as Bruton’s disease is when mature B cells are absent. There are no plasma cells.
How do X linked agammaglobunlinaemias present?
Recurrent bacterial infections in boys aged 4 months to 2 years
Name some primary B cell deficiencies
- common variable immunodeficiency
- x linked agammaglobulinaemia
- Autosomal recessive Hyper IgM syndrome
- IgA Deficiency
- IgG subclass Deficiency
- Transient Hypogammaglobulinaemia of infancy
what is common variable immunodeficiency (CVID)?
Primary B cell deficiency.
recurrent bacterial infections with higher incidence of autoimmune diseases such as thrombocytopenic purpura, and pernicious anaemia.
What is autosomal recessive hyper IgM syndrome?
Normal or High serum IgM levels BUT and absence of other isotopes.
-as well as bacterial infections susceptible to Pneumocystis jirovecii pneumonia as T cell function is impaired.
What is selective IgA deficiency?
It is the commonest primary defect.
-Undetectable IgA but normal IgG/IgM
