Human Health & Disease: Quick Review (10 Sentences)

HIV is a retrovirus that carries reverse transcriptase to convert its RNA genome into DNA, which integrates into the host cell, and it selectively destroys CD4+ T-helper lymphocytes, causing AIDS; ELISA is the screening test and Western blot is confirmatory.
Malaria is caused by Plasmodium vivax (48-hour fever cycle, benign tertian) and P. falciparum (malignant tertian, most lethal), both transmitted by the female Anopheles mosquito; haemozoin released during RBC rupture triggers the cyclic fever.
Filariasis (elephantiasis) is caused by Wuchereria bancrofti transmitted by the Culex mosquito (NOT Anopheles), which blocks lymphatic vessels causing chronic swelling of the lower limbs.
Typhoid is caused by Salmonella typhi infecting the small intestine, confirmed by the Widal test, while pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae filling alveoli with fluid.
Innate immunity comprises four non-specific barrier types: physical (skin), physiological (lysozyme, stomach acid), cellular (macrophages, NK cells), and cytokine (interferons); it is immediate but has no memory.
Adaptive humoral immunity uses B-lymphocytes that differentiate into plasma cells secreting antibodies (IgA, IgD, IgE, IgG, IgM), while cell-mediated immunity relies on T-lymphocytes; both arms produce memory cells.
Active immunity involves the body producing its own antibodies (slow onset, long-lasting, memory cells formed), whereas passive immunity involves receiving preformed antibodies (immediate, short-lived, no memory cells).
IgG crosses the placenta providing transplacental passive immunity; IgA is in colostrum providing mucosal protection to newborns; IgE is involved in allergic responses via IgE-coated mast cells releasing histamine.
Cancer arises when oncogenes (activated proto-oncogenes) drive uncontrolled cell division and tumour suppressor genes (p53, Rb) are inactivated; benign tumours are localised while malignant tumours metastasise via blood or lymph.
Key drugs of abuse: heroin (diacetylmorphine, CNS depressant) from Papaver somniferum; cocaine (CNS stimulant, blocks dopamine reuptake) from Erythroxylum coca; cannabinoids from Cannabis sativa; nicotine from tobacco causes lung cancer.