Identification of Human Blood and Tissue T Follicular Regulatory (Tfr) Cells by Flow Cytometry.

T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells are crucially involved in the regulation of germinal center reactions. Thus, as key players, the assessment of these cell subsets is necessary for a better understanding of the humoral immune response. Flow cytometry (FC) is one of the most used techniques to perform immunophenotypic analysis, allowing the simultaneous study of different proteins by using multicolor fluorescent panels. Here, we describe an approach to identify Tfr cells from human blood and tissues, namely tonsil and lymph node, by flow cytometry.