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Immune System
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Immune System

T Cells

Helper and Killer Cells

An immature T cell, a mature helper T cell, and a mature cytotoxic T cell.
An immature T cell, a mature helper T cell, and a mature cytotoxic T cell. Credit: NIAID.

Killer Cells

Killer cell makes contact with target cell, trains its weapons (target-oriented granules) on the target, then strikes.
Killer cell makes contact with target cell, trains its weapons on the target, then strikes. Credit: NIAID.

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The print version is available: Understanding the Immune System: How It Works (PDF). All artwork is by Jeanne Kelly and may not be repurposed.