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Introduction to Innate and Adaptive Immunity

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The human immune system is a complex defense mechanism that protects the body from harmful pathogens and foreign substances. It comprises two crucial components: innate and adaptive immunity.
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Related Experiment Video

Updated: May 29, 2026

Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling

Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling

Published on: July 26, 2017

Two signal models in innate immunity.

Mary F Fontana¹, Russell E Vance

¹Division of Immunology & Pathogenesis, Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720, USA.

Immunological Reviews

|September 3, 2011

Summary

This summary is machine-generated.

Innate immune responses to pathogens often require two signals for activation. This two-signal model ensures appropriate responses to infections, preventing self-damage.

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Dissecting Innate Immune Signaling in Viral Evasion of Cytokine Production

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Published on: March 2, 2014

Area of Science:

Immunology
Microbiology

Background:

The classic two-signal model of T-cell activation involves T-cell receptor engagement (signal one) and costimulatory ligands (signal two).
This model ensures T-cell responses are initiated only against genuine infectious threats.

Purpose of the Study:

To explore the role of two-signal models in innate immune responses to pathogens.
To discuss how the innate immune system integrates multiple signals for effective pathogen response, using Legionella pneumophila as a model.

Main Methods:

Review of studies on innate immune responses.
Utilizing Legionella pneumophila as a model intracellular bacterial pathogen.

Main Results:

Initiation of innate immune responses often requires two signals: a microbe-derived ligand (signal one) and contextual information (signal two).
Signal one alone can initiate many innate responses, but certain responses, especially those risking self-damage, necessitate two signals.

Conclusions:

The innate immune system integrates multiple signals to mount effective responses against bacterial pathogens like L. pneumophila.
A two-signal requirement for certain innate responses acts as a safeguard against inappropriate activation and potential self-damage.