Within the individual disease groups, levels of CD45+ CD34+CD11b+ cells and mature fibrocytes correlated significantly within HC, RA, ILD and RA-ILD but not in patients with severe asthma (HC (r = 0.76, p = 0.01), RA (r = 0.70 p = 0.02), severe asthma (r = 0.56, p = 0.15), ILD (r = 0.83, p = 0.01), RA-ILD (r = 0.85, p = 0.003). Here, CD34 is linked to interstitial lung disease.