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Overview of the Immune System

Updated: Apr 3, 2019



Disease-causing or harmful microorganisms


Material that can trigger an immune response (aka something inflammatory cells use to identify a cell as "good" or "bad")


The response to tissue damage

Presents with four classical clinical signs:

  1. Redness (RUBOR)

  2. Heat (CALOR)

  3. Swelling (TUMOR)

  4. Pain (DOLOR)

  5. BONUS= Loss of function (FUNCTIO LASEA)


a chemical signal produced by damaged cell to alert the body to danger and act as a homing signal for immune cells to come to the site of injury



1) Innate Immunity–

Non-specific, Fast, Neutrophils (PMNs)

  • First line of defense against "bad guys". These include physical barriers (such as the skin's epidermal surface) or chemical barriers (such as Chemokines produced by the damaged cell to alert the the body to danger and help recruit inflammatory cells to the site of injury)

  • Neutrophils are the first type of phagocytic cell to arrive in response to the chemokines (aka chemotactic response/cry for help)

  • Monocytes arrive and mature into macrophages which engulf and destroy pathogens. Macrophages will play an important role later on by helping to activate the adaptive branch of immunity by presenting the antigens to T-cells and continuing to make inflammatory mediators.

2) Adaptive Immunity–

Specific, Slow, Systemic, Memory, Monocytes (lymphocytes)

- Humoral immunity

  • B cells (matured into activated plasma cells) → produce antibodies (Y-shaped proteins) → → antibodies bind toxins/microbesneutralize the threat & attract T cells/other immune cells to the area to help destroy the pathogen.

  • Antibodies also play a significant role in the complement system which will be thoroughly discussed in a separate post.

- Cell-mediated immunity

  • Cytotoxic T cells (CD8) recognize infected cells and kill them

  • Helper T cells (CD4) as the name implies, they help other cells by releasing chemical signals (cytokines & chemokines) and activating various immune cell types



These notes were adapted and modified from the awesome medical education website, This is a GREAT website for visual learners. Please subscribe to their website to view the complete lecture and see step by step drawings and charts.

Use coupon code ZXG2DM8ZJ to get 15% off your subscription. Click HERE to subscribe (link opens in new tab).

Reference: Immune System Overview lecture


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