Interestingly, TNF-α, which also may trigger IL-8 expression and contribute to neutrophil influx, was significantly increased only in PAN but not in LB/ARAD, suggesting that the pathogenesis of these two CLAD phenotypes may have different backgrounds; however, further studies are required to identify the mechanistic differences between these two phenotypes. Here, CXCL8 is linked to polyarteritis nodosa.