⚡ Quick Revision : Immunity & Defense
1. The Body's Three Lines of Defense
Our body protects itself against pathogens through a hierarchical system:
- 🛡️ First Line (External): Physical barriers like the Skin, Mucus, and Stomach Acid ($HCl$).
- 🛡️ Second Line (Internal/Non-specific): Phagocytosis (WBCs engulfing germs) and Inflammation (swelling/fever).
- 🛡️ Third Line (Specific): The production of Antibodies by specialized lymphocytes to target specific germs.
2. Types of Immunity
Immunity is the resistance to the onset of a disease after infection by harmful germs.
A. Innate (Natural) Immunity:
Inherited by birth; it is non-specific (e.g., humans are naturally immune to many plant diseases).
B. Acquired Immunity:
- Active: Body produces its own antibodies (e.g., after recovering from Measles or after Vaccination).
- Passive: Ready-made antibodies are injected (e.g., Anti-tetanus serum or breast milk for infants).
3. Key Biological Terms
| Term | Definition |
|---|---|
| Antigens | Foreign substances (germs) that stimulate an immune response. |
| Antibodies | Proteins (Immunoglobulins) produced by WBCs to neutralize antigens. |
| Antiserum | Blood serum containing specific antibodies used for passive immunity. |
Question: Why is breastfeeding highly recommended for newborns?
Answer: Colostrum (the first milk) contains ready-made antibodies from the mother. This provides passive immunity to the infant whose own immune system is not yet fully developed.
Active immunity lasts a long time because the body "remembers" how to fight the germ. Passive immunity is fast but temporary because the injected antibodies are eventually broken down.
⚡ Quick Revision : Vaccines & Antibiotics
1. Vaccination & Immunization
Vaccination is the practice of introducing a vaccine into the body to produce immunity to a specific disease. A vaccine is a preparation consisting of killed or weakened germs.
Types of Vaccines:
- Killed Germs: TAB for typhoid, Salk's vaccine for poliomyelitis.
- Living Weakened Germs: BCG for tuberculosis, OPV (Oral Polio Vaccine).
- Toxoids: Extracted toxins of bacteria that are made harmless (e.g., DPT for Diphtheria, Pertussis, and Tetanus).
2. Antibiotics
Antibiotics are chemical substances produced by micro-organisms (like fungi and bacteria) which can kill or inhibit the growth of other disease-causing micro-organisms.
- Discovery: Penicillin was the first antibiotic discovered by Alexander Fleming (1928) from the mold Penicillium notatum.
- Broad-spectrum Antibiotics: These can kill a wide variety of different bacteria (e.g., Streptomycin, Tetracycline).
3. Other Medical Aids
- Sulphonamides (Sulpha Drugs): Synthetic chemical drugs that are effective against bacterial diseases (e.g., Sulphadiazine).
- Antiseptics: Chemical substances applied to the body to kill/prevent growth of germs (e.g., Tincture iodine, Dettol).
- Disinfectants: Strong chemicals used on non-living objects (drains, floors) to kill germs (e.g., Lysol, high concentration Phenol).
Question: Why shouldn't antibiotics be taken without a doctor's prescription?
Answer: Indiscriminate use of antibiotics can lead to Antibiotic Resistance, where bacteria evolve to survive the drug. It can also kill beneficial bacteria in our gut, leading to further health complications.
Antiseptics are mild and safe for skin (like Dettol), while Disinfectants are too harsh for living tissue and are used for floors and toilets.