Abstract
The activation and differentiation of CD4(+) T cells play a critical role in establishing and subsequently controlling protective adaptive immune responses. Flow cytometry is a powerful technique with which to assess the potential of xenobiotics to influence CD4(+) T cell activation and differentiation. With flow cytometry, cells are stained with fluorochrome-conjugated antibodies and/or specific fluorescent probes to assess T cell activation, proliferation, effector cytokine production, and transcription factor expression. This technique allows for complex phenotypic analysis of tens to hundreds of thousands of individual cells very rapidly to assess the potential impact of a xenobiotic on CD4 effector differentiation and activation state.