8. HUMAN HEALTH AND
DISEASES
Allergies
§ It is the exaggerated response of the immune system to certain antigens present in the environment.
§ Allergens:
Substances causing allergy. E.g. mites in dust, pollens, animal dander, fur
etc.
§ Antibodies produced against the allergens are IgE type.
§ IgE
binds on mast cells to release chemicals like histamine and serotonin
from them.
It results in allergic reactions.
§ Symptoms:
Sneezing, watery eyes, running nose, difficulty in breathing, wheezing, skin
rashes etc.
§ Determination
of cause of allergy: The patient is exposed
to or injected with very small doses of possible allergens, and the reactions
studied.
§ Treatment:
Drugs like anti-histamine, adrenaline and steroids quickly reduce the symptoms of allergy.
§
Asthma
is a respiratory
disease due to allergy.
§ Modern-day
life style and protected environment
provided early in life result in low immunity and more sensitivity to
allergens. So, many children in metro
cities suffer from allergies and asthma.
Autoimmunity
- In
higher vertebrates, memory-based acquired immunity evolved based on the ability
to differentiate foreign organisms from self-cells.
-
Sometimes, due to genetic and
other unknown reasons, the body attacks self-cells resulting in damage to the
body. It is called auto-immune disease. E.g. Rheumatoid
arthritis.
AIDS (Acquired Immuno Deficiency Syndrome)
§ It
is the deficiency of immune system.
§ Syndrome
means a group of symptoms.
§ It
is caused by HIV (Human Immunodeficiency Virus), a retrovirus
having RNA genome.
§ AIDS
was first reported in America (1981).
§ In
the last 25 years, it killed over 25 million persons.
Transmission:
§ Sexual
contact with infected person.
§ Transfusion
of contaminated blood & blood products.
§ Sharing
of infected needles.
§ From
infected mother to her child through placenta.
High risk people of getting HIV:
§ Individuals
with multiple sexual partners.
§ Drug
addicts who take drugs intravenously.
§ Individuals
who require repeated blood transfusion.
§ Children
born to an HIV infected mother.
HIV
does not spread by touch or physical contact. It spreads only through body
fluids.
There
is a time-lag (from few months to 5-10 years) between the infection and
appearance of symptoms.
Replication of retrovirus:
Life cycle of HIV:
HIV enters body → To
macrophages (acts as HIV factory) → RNA genome replicates in presence of Reverse transcriptase to form viral DNA
→ Viral DNA incorporates into host DNA→ Infected cells produce virus particles → HIV enters into helper T-cells (TH
lymphocytes) → Replicates & produce progeny viruses → Attack other TH
cells → TH cells decrease → Weaken immunity.
§ During this period, the person suffers from fever,
diarrhoea and weight loss.
§ Due to deficiency of TH
cells, he may be infected with
Mycobacterium, viruses, fungi &
parasites like Toxoplasma.
§ Diagnosis: ELISA test
(Enzyme-linked immuno-sorbent Assay).
§
Treatment:
Anti-retroviral drugs are partially effective. They can only prolong the life
of the patient.
Prevention of AIDS:
o
Educate people about AIDS
through organisations like National AIDS Control Organisation (NACO), non-governmental
organisations (NGOs), WHO etc.
o
Make blood (from blood
banks) safe from HIV.
o
Use disposable needles
and syringes.
o
Advocate safe sex and
free distribution of condoms.
o
Control drug abuse.
o Regular check-ups for HIV in susceptible population.
Thank you💕
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