Transcription Factor Evaluation by Flow Cytometry.

The development of T helper (Th) cell subsets requires activated T cells that respond to a polarizing cytokine environment, resulting in the activation and expression of specific transcription factors. The subset-specific transcription factors are located either in the cytoplasm or in the nucleus, which determine the functional profile of Th populations, inducing the production of specific effector cytokines and functions. Flow cytometry analysis of transcription factors has become very common not only in research but also in immunologic follow-up protocols of patients recruited in clinical trials (as evaluation of CD4+CD25+ FOXP3+ T regulatory cells). Here, we propose and describe one-step protocols to evaluate the expression of transcription factors in mouse and human CD4+ lymphocytes, focusing the critical points of this cytometric approach.