Hypersensitivity and the lung Flashcards
What is innate immunity?
E.g. sputum and cilia in lungs
- It is the first line in defence and has an immediate response.
- It is composed of phagocytes, mast cells
What is innate immunity?
E.g. sputum and cilia in lungs
- It is the first line in defence and has an immediate response.
- It is composed of phagocytes, mast cells
What is adaptive immunity?
E.g. Pus, swelling, granuloma
- Often the second line
- Delayed response time, often > 4 days
- B and T -lymphocytes
What are the cellular components of the immune system?
- Phagocytes e.g. monocytes and neutrophils
- Lymphocytes: make and release antibodies and kill diseased cells
What are the humoral components of the immune system?
- Immunoglobulins
- Complement (form membrane attack complex)
- Cytokines (allow communication between WBC and tissue cells)
What are antibodies produced by?
B-lymphocytes (plasma cells)
What do antibodies do?
- Neutralise or eliminate pathogens
- Can also cause disease
What are the 5 classifications of antibodies?
IgM, IgG, IgE, IgA, IgD
What are IgM antibodies?
they are circulating tetramers (a molecule (as an enzyme or a polymer) that consists of four structural subunits) made at the beginning of infection
What are IgG antibodies?
Monomer highly specific antibodies targeting single epitopes (pathogenic site)
What are IgE antibodies?
Likely to have developed in response to parasitic threats. Implicated in allergy, particularly alongside eosinophils
What are IgA antibodies?
Expressed in mucosal tissue. Forms dimers (a pair or them stuck together). Protects the neonatal gut
What are IgD antibodies?
Monomers, induction of antibodies in B cells, activates basophils and mast cells
What is Type I hypersensitivity?
- Mediated by IgE antibodies (+ eosinophils)
- Immediate (within an hour)
E.g. anaphylaxis and hay fever
What is Type II hypersensitivity?
- Mediated by cytotoxic antibodies bind to the cell antigen
- Comes on in hours to days
E.g. Transfusion reactions and Goodpastures (Anti GBM disease) - antibodies attack the basement membrane in lungs and kidneys
What is Type III hypersensitivity?
- Mediated by deposition of immune complexes
- Comes on typically 7-21 days
E.g. Hypersensitivity pneumonitis; post streptococcal glomerulonephritis
What is Type IV hypersensitivity?
- Mediated by T-Cells (lymphocytes)
- Takes days to weeks or months to come on
E.g. Tuberculosis; Stevens-Johnson syndrome
How does Type I hypersensitivity cause a reaction?
- Antigen interacts with IgE bound to mast cells or basophils
- Degranulation of mediators lead to local effects
- Histamine is the predominant mediator
What is anaphylaxis?
- Sudden onset
- Systemic degranulation of mast cells and histamine release
- Skin, eyes, lips swelling, hypotension
- Bronchospasm can result in airway occlusion and death if not managed
(Type I Hypersensitivity)
How to manage anaphlyaxis?
- Adrenaline 0.5mg or auto injector
- Steroids
- Antihistamines
- Second peak may occur after 12 hours
- Measure tryptase
How does Type II hypersensitivity cause a reaction?
- Antibodies reacting with antigenic determinants on the host cell membrane
- Usually IgG or IgM
- Outcome depends on whether complement is activated and if metabolism of cell is affected
What is Anti-Glomerular Basement Membrane Disease
- Rare but deadly Type II HS disease
- Alveolar involvement
- GBM made of type IV collagen present in alveoli
- The Alpha 3 subunit of this collagen becomes antigenic
Very rare
How do we treat AGBMD?
- With plasmapheresis (remove plasma to extract offending Abs)
- Immune suppression (Steroids)
- Supportive lung treatment (ventilation) and kidneys (filtration)
What is Mycoplasma Pneumonia?
- Type II HS
- Antibodies also attack red blood cells causing agglutination and haemolysis (rupture and destruction of RBC)
