Vaccines, antibiotics, allergens, autoimmunity

1. Introduction to the Immune System

The immune system protects the body from harmful pathogens like bacteria, viruses, fungi, and toxins.
It consists of specialized cells, tissues, and organs that help in defense mechanisms.
Key components include White Blood Cells (WBCs), antibodies, lymphatic system, bone marrow, thymus, spleen.
Immunity is classified into innate immunity (non-specific defense) and adaptive immunity (specific defense).

A vaccine is a biological preparation that provides immunity against a specific disease.
It contains weakened or killed pathogens or parts of a pathogen (antigen) to stimulate the immune system.
Vaccines help the body produce memory cells for long-term immunity.
Types of vaccines:
- Live attenuated vaccines: Contain weakened pathogens (e.g., MMR, BCG).
- Inactivated vaccines: Contain killed pathogens (e.g., Polio, Rabies).
- Subunit vaccines: Contain only specific parts of a pathogen (e.g., Hepatitis B).
- mRNA vaccines: Use genetic instructions to produce an immune response (e.g., COVID-19 vaccines like Pfizer, Moderna).
Herd immunity is achieved when a large percentage of the population is vaccinated, reducing disease spread.

Antibiotics are drugs used to treat bacterial infections by killing bacteria or inhibiting their growth.
They are ineffective against viral infections like the common cold and flu.
Common antibiotics include penicillin, amoxicillin, tetracycline.
Mechanism of action:
- Bactericidal antibiotics: Kill bacteria (e.g., Penicillin).
- Bacteriostatic antibiotics: Prevent bacterial growth (e.g., Tetracycline).
Antibiotic resistance occurs when bacteria mutate and become resistant to drugs, making infections harder to treat.
Overuse and misuse of antibiotics lead to superbugs (e.g., MRSA - Methicillin-resistant Staphylococcus aureus).

Allergens are harmless substances that trigger an overreaction of the immune system.
Common allergens include pollen, dust, certain foods, insect stings, animal dander.
The immune system releases histamines, causing symptoms like sneezing, itching, and swelling.
Common allergic conditions:
- Hay fever (caused by pollen).
- Asthma (triggered by allergens, dust, smoke).
- Food allergies (e.g., peanuts, shellfish, dairy).
- Anaphylaxis: A severe, life-threatening allergic reaction requiring immediate medical attention.
Antihistamines are used to manage allergic reactions.

Autoimmune diseases occur when the immune system mistakenly attacks the body's own cells.
The exact cause is unknown but may involve genetic and environmental factors.
Common autoimmune disorders:
- Rheumatoid arthritis: The immune system attacks joints, causing pain and swelling.
- Type 1 diabetes: The immune system destroys insulin-producing cells in the pancreas.
- Lupus: Affects multiple organs, leading to inflammation and tissue damage.
- Multiple sclerosis: The immune system damages nerve coverings, affecting muscle control.
Autoimmune diseases are treated using immunosuppressive drugs to reduce immune system activity.

A strong immune system helps prevent infections and diseases.
Ways to boost immunity:
- Eat a balanced diet with vitamins and minerals.
- Get regular exercise to enhance immune function.
- Avoid smoking, alcohol, and stress.
- Get adequate sleep to support immune processes.

The immune system is essential for protecting the body against infections.
Vaccines play a crucial role in preventing diseases and improving immunity.
Antibiotics are used to treat bacterial infections but should be used responsibly to avoid resistance.
Allergens cause allergic reactions that can range from mild to life-threatening.
Autoimmune diseases occur when the immune system attacks the body, requiring medical management.