A brief history of T cell help to B cells

The role of T cell help to B cells was discovered only a few years after the discovery of B cells. In this Timeline article, the author describes the key events that led to the identification of T follicular helper (TFH) cells as the main T helper cell type for B cells. In celebration of the 50th anniversary of the discovery of B cells, I take a look back at the history of T cell help to B cells, which was discovered 47 years ago. In addition, I summarize and categorize the distinct molecules that are expressed by CD4+ T cells that constitute 'help' to B cells, and particularly the molecules expressed by T follicular helper (TFH) cells, which are the specialized providers of help to B cells.