Lesson 13 of 13 · 13 min

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Must-know facts

20 facts

1Health: complete physical, mental and social well-being, not just the absence of disease.
2Typhoid: Salmonella typhi, fever 39° to 40°C, confirmed by the Widal test; Mary Mallon was a carrier.
3Pneumonia: Streptococcus pneumoniae and Haemophilus influenzae, alveoli fill with fluid; lips and nails turn grey to bluish in severe cases.
4Common cold: rhino viruses, nose and respiratory passage but not lungs, 3-7 days.
5Malaria: sporozoites enter by the bite of a female Anopheles; haemozoin from bursting RBCs causes chill and fever every 3-4 days; P. falciparum causes malignant malaria.
6Amoebiasis: Entamoeba histolytica in the large intestine; houseflies are mechanical carriers.
7Filariasis (elephantiasis): Wuchereria bancrofti and W. malayi in lymphatic vessels of the lower limbs, spread by female mosquitoes.
8Ringworm fungi: Microsporum, Trichophyton, Epidermophyton.
9Gambusia fish eat mosquito larvae; Aedes spreads dengue and chikungunya.
10Innate barriers: physical, physiological, cellular, cytokine (interferons).
11Antibody: H2L2, two light and two heavy chains; IgA, IgM, IgE, IgG.
12B cells make antibodies (humoral); T cells mediate CMI and graft rejection.
13Colostrum carries IgA: passive immunity. Tetanus antitoxin and snake antivenom are passive immunisation.
14Hepatitis B vaccine is made in yeast by recombinant DNA technology.
15Allergy: IgE, histamine and serotonin from mast cells; treated with anti-histamine, adrenalin, steroids.
16Primary lymphoid organs: bone marrow and thymus. Secondary: spleen, lymph nodes, tonsils, Peyer's patches, appendix. MALT is about 50% of lymphoid tissue.
17HIV: retrovirus; macrophage is the HIV factory; helper T cells fall; ELISA detects; time-lag usually 5-10 years.
18Cancer cells lose contact inhibition; metastasis defines malignant tumors; α-interferon is a biological response modifier.
19Heroin: diacetylmorphine from morphine of Papaver somniferum, a depressant. Cocaine: Erythroxylum coca, blocks dopamine transport.
20Nicotine releases adrenaline and nor-adrenaline; smoking raises CO and lowers haem-bound oxygen.

Common traps

Where marks are lost

Saying the common cold infects the lungs.

Rhino viruses stay in the nose and respiratory passage and spare the lungs; pneumonia is the disease of the alveoli.

Blaming the mosquito's bite for the malarial fever.

The chill and fever come with RBCs bursting and releasing haemozoin, every three to four days.

Calling the mosquito that spreads filariasis Anopheles, or the one spreading dengue Culex.

NCERT only says female mosquito vectors for filariasis; dengue and chikungunya are spread by Aedes. Anopheles carries Plasmodium.

Calling colostrum or maternal antibodies across the placenta active immunity.

Ready-made antibodies from outside are passive immunity; the infant made none of them.

Saying T cells secrete antibodies.

B cells secrete antibodies; T cells help B cells and mediate CMI, including graft rejection.

Listing the thymus or bone marrow as secondary lymphoid organs.

Bone marrow and thymus are primary; spleen, lymph nodes, tonsils, Peyer's patches and appendix are secondary.

Saying HIV first multiplies in helper T cells only.

It enters macrophages, which become the HIV factory, and simultaneously helper T cells, whose number falls.

Calling allergy antibodies IgG.

Allergy antibodies are IgE; IgA is the colostrum antibody.

Calling heroin a stimulant.

Heroin is a depressant that slows body functions; cocaine is the stimulant.

Saying a benign tumor metastasises.

Benign tumors stay where they are; metastasis belongs to malignant tumors.

Key terms

20 terms

Pathogen: An organism that causes disease, such as a bacterium, virus, fungus, protozoan or helminth.
Widal test: The test that confirms typhoid fever.
Sporozoite: The infectious form of Plasmodium injected by an infected female Anopheles.
Haemozoin: Toxic substance released when infected RBCs burst, causing the recurring chill and fever of malaria.
Vector: An organism that carries a pathogen to a new host, such as the female Anopheles for malaria.
Interferon: Protein secreted by virus-infected cells that protects non-infected cells from the virus.
Anamnestic response: The strong secondary immune response to a pathogen met before.
Humoral immune response: The antibody-mediated response, so named because antibodies are in the blood.
Cell-mediated immunity: The T-lymphocyte-mediated response, responsible for graft rejection.
Colostrum: The yellowish first milk, rich in IgA antibodies for the newborn.
Antitoxin: A preparation of antibodies against a toxin, injected for quick protection as in tetanus.
Allergen: An environmental substance that triggers an allergic, IgE-type response.
Auto-immune disease: Damage caused when the body's immune system attacks its own cells, such as rheumatoid arthritis.
MALT: Mucosa-associated lymphoid tissue in the linings of the major tracts, about half of all lymphoid tissue.
Retrovirus: An enveloped RNA virus that copies its genome into DNA using reverse transcriptase.
Contact inhibition: The stop signal normal cells receive from touching neighbours; cancer cells lose it.
Metastasis: Spread of malignant tumor cells through blood to start tumors at distant sites.
Proto-oncogene: A normal cellular gene (c-onc) that can cause cancer when activated under certain conditions.
Addiction: Psychological attachment to the effects of a drug or alcohol.
Dependence: The body's withdrawal syndrome when regular drug or alcohol use is stopped abruptly.

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