Immunology Flashcards
What is the immune system for?
To identify and eliminate micro-organisms and other harmful substances
When should you think about iimmune deficiency with a patient?
When a patient presents with SPUR infections: Serious Persistent Unusual Recurrent
How do you define a serious infection?
Unresponsive to oral antibiotics
How do you define a persistent infection?
There is early structural damage
Chronic infections
How do you define an unusual infection?
Unusual organisms and sites
How do you define a recurrent infection?
Two major or one major and recurrent minor infections in one year
Bar SPUR, what are other features that are suggestive of primary immune deficiency?
- Weight loss/failure to thrive
- Eczema
- Chronic diarrhoea
- Mouth ulceration
- Family history
How do you classify immunodeficiencies?
Primary - rare
Secondary - common, often subtle, often involves more than one component of the immune system
What are the two arms of the immune system?
Innate and Adaptive - detect and destroy pathogen in different ways
What cells are involved in the innate immune system?
Macrophages, neutrophils, mast cells and NK cells
Which proteins are involved in the innate immune system?
Complement, Acute phase proteins and cytokines
What is different about the innate immune system?
Recognises structures that are unique to infectious organisms
Essentially identical responses in all individuals
What are the functions off the innate immune system?
- Rapid clearance of micro-organisms
- Stimulates the acquired (adaptive) immune response
- Buys time whilst the acquired immune system is mobilised
What are the cells of the acquired immune system?
B & T lymphocytes
What are the proteins of the acquired immune system?
Antibodies
What is unique about the acquired immune system?
- Repertoire isn’t genetically encoded
- Acquired as a response to exposure to an antigen
- Responsive to an unlimited number of molecules
- Very specific
- Memory
Which cells are the phagocytes?
Neutrophils and macrophages
What are the functions of phagocytes?
Initiation and amplification of inflamm response
Scavenging of cellular and infectious debris
Ingest and kill micro-organisms
Resolution and repair
Phagoyctes are particularly important in defence against which pathogens?
Bacteria and fungi
What are the clinical features of phagocyte deficiencies?
Recurrent infections - may affect common and unusual sites
Commonly fungal infections (oral candida)
What is Kostmann syndrome?
Rare autosomal recessive disorder
What is the clinical presentation of Kostmann syndrome?
Infections usually within 2 weeks after birth - recurrent bacterial infection, systemic or localised infection
What are the non specific features of Kostmann syndrome?
fever, irritability, oral ulceration and failure to thrive
What are the supportive treatments of Kostmann syndrome?
Prophylactic antibiotics and antifungals
What is the definitive treatment of Kostmann syndrome?
Stem cell transplantation
Granulocyte colony stimulating factor - specific growth factor to assist maturation of neutrophils
What is leukocyte adhesion deficiency?
Rare primary immunodeficiency that’s caused by a genetic defect in leukocyte integrins (CD18)
What is the classical clinical presentation of leukocyte adhesion deficiency?
Characterised by marked leukocytosis and localised bacterial infections that are difficult to detect
What are the three main types of pathogen recognition receptors?
Toll like receptors
Scavenger receptors
Lectin receptors
What are opsonins?
Molecule that act as binding enhancers for the process of phagocytosis (include complement C3b, IgG antibody and CRP)
How do opsonins work?
Bind to receptors on phagocyte surface
Phagocytes express Fc receptors - allow binding of antibody that is also bound to antigen
What is chronic granulomatous disease?
Failure of oxidative killing mechanisms - deficiency of the intracellular killing mechanism of phagocytes - inability to generate oxygen free radicals
How are the granulomas formed in chronic granulomatous disease?
Inability to clear organisms - excessive inflammation - persistent accumulation of neutrophils, macrophages and lymphocytes
What are the features of chronic granulomatous disease?
Recurrent deep bacterial infections (especially staphylococcus, aspergillus, pseudomonas cepacia) Recurrent fungal infections Failure to thrive Lymphadenopathy and hepatosplenomegaly Granuloma formation
