Differentiate between innate and acquired immunity. Describe the structure of an antibody and the two types of acquired immune response.

1. 1 · Define immunity. Immunity is the ability of the body to fight disease-causing organisms, given by the immune system.
2. 2 · Innate immunity. Non-specific, present at birth; four barriers: physical (skin, mucus), physiological (acid, saliva, tears), cellular (neutrophils, monocytes, NK cells, macrophages), cytokine (interferons).
3. 3 · Acquired immunity. Pathogen-specific with memory; primary response is weak, secondary (anamnestic) response is strong.
4. 4 · Antibody structure. Y-shaped, two heavy and two light chains (H₂L₂), disulphide bonds, antigen binding sites; IgA, IgM, IgE, IgG.
5. 5 · Draw the antibody. [Diagram: Y-shaped antibody with heavy chain, light chain, S-S bonds, antigen binding sites, N and C ends; variable and constant regions are extra labels]
6. 6 · Two responses.
   • Humoral: B-lymphocytes make antibodies in the blood.
   • Cell-mediated: T-lymphocytes; graft rejection; need for tissue matching and immunosuppressants.
7. 7 · Close in one line. So innate immunity is the first line of defence, and acquired immunity gives specific, lasting protection.

Scoring tip: Give one example for every barrier, and label at least the heavy chain, light chain and antigen binding site on the antibody.