9: Immunology 2: Vaccination, Hypersensitivity, and Ageing Flashcards
Active Immunisation
The individual is exposed to pathogen or antigen, these stimulate the immune system, and the body creates its own antibodies
Passive Immunisation
Antibodies are created in one individual and then transferred to another
Toxoid Vaccines
- Bacterial exotoxins that have been inactivated or suppressed via heat or chemicals
- Highly immunogenic
- Used for tetanus, botulism and diphtheria
Subunit Vaccines
- Contains the particular antigenic determinant of the pathogen
- Non-living so very safe
- Poor immuno-memory – limited stimulation of the immune system
Herd Immunity
- The vaccination of a significant enough proportion of the population to offer protection to the population as a whole
- Disruption of the chain of infection
- The more immune individuals, the lower the chance of contacting an infected individual
Problems with Vaccines: Adverse Effects
- Allergy to preservatives
- Reversion to virulence
- Local hypersensitivity reactions (toxoids)
Innate Immune Cells that Drive Hypersensitivity: Basophils
Activated function:
Promotion of allergic responses and augmentation of anti-parasitic immunity
Innate Immune Cells that Drive Hypersensitivity: Mast Cells
Release of granules containing histamine and active agents
Innate Immune Cells that Drive Hypersensitivity: Eosinophils
Killing of antibody-coated parasites
Hypersensitivity: Type I - Allergy
- Most common type
- Rapid onset, short-term
- Local or systemic
- Induced by antigens (allergens) which activate B-cells to secrete antibodies
- Antibodies secreted are of the IgE type (usual antibody secretion is IgG or IgM)
Hypersensitivity: Type II - Cytotoxic
- Antibody-mediated cellular destruction
- May induce direct cellular lysis (complement-mediated)
- Antibodies may enhance phagocytic activity
- Examples: ABO transfusion reaction, rhesus incompatibility, drug-induced haemolytic anaemia
Hypersensitivity: Type III - Immune Complex-Mediated
- Accumulation of antibody-antigen complexes in the circulation and tissues
- Effects depend on location of complexes, but they attract phagocytes – release of lytic enzymes and cytokines and activate complement
- Can be local or systemic
- Examples: serum sickness, rheumatoid arthritis, drug reactions
Hypersensitivity: Type IV - Delayed Type
- Delay is 1-3 days (generally peaks 48-72 hours after exposure)
- Not antibody-mediated but cell-mediated – produced by T-cells interacting with antigens
- Delayed because specific T-cells must migrate to location of antigen before inflammation develops
- May be prolonged & result in formation of granulomas e.g. tuberculosis
- Examples: contact dermatitis
How Does Ageing Affect Immune Function? (Four Effects)
- Greatly reduced production of thymic hormone (important for the maturation of T-cells)
- Reduced responsiveness of T-cells to antigens
- Reduced responsiveness of B-cells
- Decline in immune surveillance
Ageing and Immune Cells
- Macrophages, neutrophils, and natural killer cells decline in function
- Leads to deficiencies in innate immunity & increased incidence of cancers due to decline in immune surveillance
