B cells are Essential for Memory T cell Development in Germinal Centers

Nature recently listed 20 major T cell milestones since the early breakthroughs of Drs. Jacques Miller and Max Cooper. However, to make the story more complete, several key discoveries may need to be mentioned. One of the major missing episodes is the discovery of the bone marrow in mice as the origin of T and B cells, revealed by Dr. Henry Claman and his colleagues. The complete absence of the critical role of B cells in the final differentiation of T cells into memory lineages could be a major oversight in modern immunology. In this short essay, I will try to summarize some of the published evidence showing that T cell differentiation into memory cells is triggered only by B cells in germinal centers after priming at infection sites for CD8 T cells and in the T cell zone for CD4 T cells in the spleen and draining lymph nodes. Based on the analysis, T cells need two steps to develop into long-lived memory cells, and a new T cell lineage model is presented.