New insights into the differentiation and function of T follicular helper cells

The seminal studies characterizing T follicular helper (T-FH) cells described a non-polarized CD4(+) T cell population with a unique ability to home to B cell follicles and to induce antibody production by B cells. In the past few years, the study of T-FH cells has enjoyed a renaissance and there has been a surge of research activity aimed at understanding the function and differentiation of these important cells. This Review focuses on the current progress in T-FH cell biology and the important questions that remain unanswered. Particular attention is paid to recent studies that support the idea that T-FH cells are a separate T cell lineage and those that probe the relationship of T-FH cells to other T helper cell subsets.