Identification of T Peripheral Helper (Tph) Cells.

T peripheral helper (Tph) cells represent a T cell population that stimulates B cell responses within peripheral tissues. Like T follicular helper (Tfh) cells, PD-1hi CXCR5- CD4+ Tph cells produce IL-21 and CXCL13, yet these cells differ from Tfh cells in expression of both transcription factors and chemokine receptors. Originally identified in rheumatoid arthritis synovium, Tph cells are expanded in multiple autoimmune diseases. Tph cells can be identified and distinguished from Tfh cells by both flow cytometry and mass cytometry. Here, we describe detailed methods to identify Tph cells and characterize associated phenotypic features and functions. These protocols and additional notes provide a guide to identify and explore the roles of Tph cells in various human diseases.