Nicastro M, Vescovini R, Maritati F, et al. - Forty-four individuals with newly diagnosed chronic periaortitis (CP, a rare disease identified by periaortic and periiliac fibroinflammatory tissue) and 30 healthy controls were examined in order to investigate the role of fibrocytes, circulating precursors of tissue fibroblasts, in individuals with CP. In patients vs controls, the frequency of circulating Col1+CD45+ fibrocytes was greater. In all analyzed biopsy samples from patients with CP, CD45+proCol1+ and CXCR4+proCol1+ cells were discovered. In patients with CP, serum levels of CXCL12 were also higher compared with controls, and tissue-infiltrating inflammatory cells strongly expressed CXCL12. Elevated serum levels of Th2 cytokines (eg, interleukin-13 [IL-13] and IL-10) were observed in individuals, and a dominant infiltration of GATA-3+ cells, also designating Th2 polarization was exhibited by immunohistochemistry, since Th2-skewed responses are recognized to promote fibrocyte differentiation. Therefore, the conclusions suggest that in the peripheral blood of patients with CP and infiltrate target lesions, fibrocytes are enriched. Furthermore, in the pathologic tissue, the gathering of fibrocytes could be prompted by CXCL12, and Th2-skewed immune responses are inclined to promote their differentiation.