Immunology and Vaccines
Immunology and Vaccines tests innate and acquired immunity, antibody structure, B and T cells, immunological memory, vaccination and immune disorders.
Core rules
- Innate immunity is non-specific and includes barriers, phagocytes, inflammation and complement.
- Acquired immunity is specific and has humoral immunity through B cells and cell-mediated immunity through T cells.
- Helper T cells recognise antigen on MHC class II and activate B cells and cytotoxic T cells; cytotoxic T cells recognise MHC class I on infected cells.
- Primary response produces IgM first and creates memory; secondary response is faster and stronger, mainly IgG.
- Active immunity develops after infection or vaccination; passive immunity is transferred ready-made antibodies, as in colostrum or antitoxin.
Worked example
A person receives tetanus antitoxin after a deep wound. This is passive immunity because antibodies are injected directly. It gives immediate protection but no memory. A tetanus toxoid vaccine would give active immunity: the modified toxin stimulates an immune response and memory cells, so protection develops after a delay but lasts longer. The reasoning turns on whether the person's own immune system makes the antibody.
Traps
- Passive immunity does not generate memory.
- Vaccines are active immunity, not antibiotics.
- Antibodies are proteins; B cells secrete them, but T cells do not.
- MHC molecules present antigen; they are not antibodies.