Immune System

Status: public · Confidence: medium (0.78) · Basis: verified_sources

## 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

- [OpenStax Biology 2e: Innate Immune Response](https://openstax.org/books/biology-2e/pages/42-1-innate-immune-response)
- [OpenStax Biology 2e: Adaptive Immune Response](https://openstax.org/books/biology-2e/pages/42-2-adaptive-immune-response)

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