Quantifying helper cell function of human TFH cells in vitro.

Blood-circulating CXCR5(+) CD4(+) T cells and T follicular helper (TFH) cells, which participate in germinal center (GC) reactions within secondary lymphoid organs, are specialized in providing help to B cells. This chapter describes ways to isolate TFH-like cells out of peripheral blood or tonsils and to quantify their B cell helper function. This comprises different co-culture approaches of TFH-like cells and B cells and the evaluation of their capacity to induce immunoglobulin secretion and plasma cell differentiation. In addition, B cell helper function of CD4 T cells can be estimated indirectly by quantifying the expression of B cell helper cytokines and co-stimulatory and TFH-associated molecules.