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 lifestyle 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 the 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 an infected person.
- Transfusion of contaminated blood and blood products.
- Sharing of infected needles.
- From infected mother to her child through placenta.
HIV does not spread by touch or physical contact. It spreads only through body fluids.
There is a time-lag (from a few months to 5–10 years) between the infection and appearance of symptoms.
High-Risk Groups for HIV
- Individuals with multiple sexual partners.
- Drug addicts who take drugs intravenously.
- Individuals who require repeated blood transfusions.
- Children born to an HIV-infected mother.
Replication of Retrovirus
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, diarrhea, and weight loss.
- Due to deficiency of TH cells, they 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
- Educate people about AIDS through organizations like National AIDS Control Organisation (NACO), non-governmental organizations (NGOs), WHO, etc.
- Make blood (from blood banks) safe from HIV.
- Use disposable needles and syringes.
- Advocate safe sex and free distribution of condoms.
- Control drug abuse.
- Regular check-ups for HIV in susceptible populations.
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