Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2019 Jul 7;25(25):3123–3135. doi: 10.3748/wjg.v25.i25.3123

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.

This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial.

PMC Copyright notice

Activation of naïve helper T cells is thought to occur through a three signal pathway. Signal 1, antigen recognition by the T cell receptor complex. Antigens are presented by major histocompatibility complex II cells [antigen presenting cells (APC) such dendritic cells]. Signal 2, co-stimulation, the interaction between the APC (CD80 and CD86) and the T cell (CD28). Signal 3, cellular proliferation and T cell differentiation into effector phenotypes (Th1, Th2), through cytokine stimulation. MHC: Major histocompatibility complex; APC: Antigen presenting cells.