Biology and Human Welfare: Disease, Immunity and Applied Biology
Biology and Human Welfare covers pathogens and disease, immunity and vaccines, cancer and drug abuse, plus applied biology in animal husbandry, plant breeding and microbes in food.
Pathogens and disease
- Plasmodium causes malaria and is transmitted by the female Anopheles mosquito; it first multiplies in liver cells, then in red blood cells.
- Entamoeba histolytica causes amoebiasis; Ascaris causes ascariasis; Wuchereria causes filariasis.
- Ringworm is caused by fungi (Microsporum, Trichophyton, Epidermophyton), not by worms.
Immunity
- Innate immunity is non-specific: barriers, phagocytes and interferons. Acquired immunity is specific and has memory, mediated by B cells (antibody-mediated) and T cells (cell-mediated).
- An antibody has two heavy and two light chains; classes are IgA, IgM, IgG, IgD and IgE.
- Active immunity follows infection or vaccination; passive immunity is transferred ready-made, as with IgA in colostrum or IgG across the placenta.
Worked example
Why does a booster dose produce a far higher antibody titre than the first dose? The first dose generates memory B and T cells. On re-exposure these proliferate rapidly and become plasma cells, giving a secondary response that is faster, larger and longer-lasting.
HIV, cancer and drugs
- HIV is a retrovirus using reverse transcriptase; it destroys helper T cells, and diagnosis uses ELISA.
- Cancer cells lose contact inhibition and metastasise; oncogenes are cellular genes that can trigger cancer.
- Opioids (morphine, heroin), cannabinoids (marijuana) and coca alkaloids (cocaine) act on the central nervous system.
Traps
- Antibiotics do not act on viruses.
- Vaccines are preventive, not curative.
- IgA in colostrum is passive immunity.