← 🫀 Human body · usually met in Std 8-12
The body's defence: barriers first, then a general response to anything foreign, then a specific response that remembers.
Skin, mucus, stomach acid and tears keep most things out. What gets past meets the innate response — white cells that engulf invaders, inflammation, fever — which is fast and the same whatever the intruder. Behind it sits the adaptive response, which identifies a specific pathogen, makes antibodies shaped to it, and keeps memory cells afterwards. That memory is why most childhood illnesses only happen once.
Vaccines use that memory deliberately. They present the immune system with a harmless version or a piece of a pathogen, so the memory cells exist before the real encounter. An allergy is the same machinery reacting strongly to something harmless, such as pollen; an autoimmune condition is it mistaking the body's own tissue for an invader.
Want to see it moving? Search YouTube for “The immune system” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.
This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.
Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus. World Health Organization ↗Health facts stated carefully, and updated when the evidence changes.Last gone through: 1 October 2026 · How these entries are written
Ask GuruAcharya Samayeshwar
