Identification of Tertiary Lymphoid Structure-Associated Follicular Helper T Cells in Human Tumors and Tissues.

Follicular helper T (Tfh) cells are major components of the humoral immune response due to their pivotal role in germinal center formation and antibody affinity maturation following B-cell isotype switching. This CD4 T-cell subtype is mainly found in the B-cell zone of secondary lymphoid organs as well as in tertiary lymphoid structures (TLS), which are highly organized structures composed of T and B cells, occasionally found at the invasive margin in the tumor microenvironment.We describe here how to perform immunofluorescence staining of tumor tissue sections and multicolor flow cytometry on tumor cell suspensions to identify and visualize these TLS-associated Tfh cells within the tumor microenvironment of various human cancers. These assays take advantage of combinations of markers and molecules involved in Tfh differentiation and function.