TNFRSF13B and B cell deficiency: Concurrently, several other factors associated with B-cell function were downregulated in HSS sufferers: ebf1a, which is crucial in B-cell development and whose disruption led to selective B-cell deficiency in zebrafish [16], tnfrsf13b (TACI), a central receptor in the APRIL/BAFF pathway suggested to have a B1-cell specific function, and tnfrsf14 (HVEM), an inhibitory receptor expressed on B- as well as T-cells [17].