CXCR4 and Langerhans cell histiocytosis: Moreover, Quispel et al also revealed that C-X-C motif chemokine receptor 4 (CXCR4) is generally expressed by LCH cells, CD1a+CXCR4+ cells could also be detected in the blood, and C-X-C motif chemokine ligand 12 (CXCL12, the ligand of CXCR4) is detected in most LCH lesions, thus the CXCR4-CXCL12 interaction may contribute to LCH cells homing and trapping in lesions [72].