These observations are consistent with the notion that the high level of CXCL12 we observed in the lung tissue of SSc-ILD patients, combined with the high level of CXCR4 we observed [13] in SSc-ILD monocytes (that is, fibrocyte precursors), leads to a relatively low steady-state number of CXCR4+/ColI+ cells in the peripheral blood and their accumulation in the lungs. Here, CXCL12 is linked to systemic sclerosis.