# Immune System
Confidence: high
Last verified: 2026-05-22
Generation: ai_assisted


## TL;DR

The immune system defends against pathogens (bacteria, viruses, fungi, parasites). Two branches: innate (immediate, non-specific — macrophages, neutrophils, complement) and adaptive (delayed, specific — B cells/antibodies, T cells). Vaccination trains adaptive immunity without causing disease.

## Core Explanation

Innate: first line (skin, mucus), inflammatory response, phagocytes engulf pathogens. Adaptive: B cells produce antibodies, T cells kill infected cells or help B cells. Memory cells: rapid response on re-exposure (basis of vaccination). Autoimmune diseases: immune system attacks self (Type 1 diabetes, rheumatoid arthritis, MS). Immunodeficiency: weakened immune system (HIV/AIDS, chemotherapy).

## Further Reading

- [Janeway's Immunobiology (9th Ed)](https://www.garlandscience.com/product/isbn/9780815345510)