TFH cells can have a dual effect on lymphoma B cells, especially of GC origin, because of their physiologic function to provide pro-survival signals (e.g. via CD40L:CD40) only to B cells that have optimally re-arranged their Ig genes and to restrain the growth of the other suboptimal clones (Basso et al., 2004; Good-Jacobson et al., 2010). Here, CD40 is linked to lymphoma.