In the GC of lymphoid organs, help provided by Tfh cells is usually limited as they are outnumbered by B cells, therefore promoting affinity maturation of B cells with the highest affinity for antigen.22 Our finding of abundant Tph cells further suggests that in the inflamed early RA ST, B cell help is readily available, potentially allowing affinity maturation of autoreactive B cell clones with low affinity, driving production of autoantibodies locally in the inflamed tissue. Here, TPH1 is linked to rheumatoid arthritis.