CCR9 and autoimmune pancreatitis: Furthermore, pDCs secretion of type I IFNs mediated by TLR9 activation was markedly augmented in the presence of CD4+CXCR3+Th1 cells, suggesting that activated CD4+CXCR3+Th1 cells act synergistically with bacterial DNA to differentiate pancreatic CCR9+pDCs that cause AIP.