Serum macrophage colony-stimulating factor (M-CSF) levels correlate with clinical response to interferon-alpha in patients with early-stage B-CLL.

Interferon-alpha (IFN-alpha) reduces peripheral lymphocyte counts in B-CLL (CLL). In eight patients with stage 0 CLL on IFN-alpha therapy, peripheral lymphocyte counts fell to 61.7 +/- 19.5% of baseline at week 2 (P < 0.01), while serum M-CSF levels rose from 455 +/- 183 U/ml to 686 +/- 110 U/ml (P < 0.05). Neopterin levels also showed a significant rise. M-CSF levels were correlated with clinical response in these patients. Increased production of M-CSF and the activation of mononuclear phagocytes may be involved in clinical responses to IFN-alpha in early-stage CLL.