IgG, IgA and IgM Autoantibodies to GM-CSF Are Present in AML, CML and MDS Patients and IgG Titer Is Associated with Disease Progression.

Neutralizing IgG antibodies to recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) have been described in patients with acquired pulmonary alveolar proteinosis (PAP) and may contribute to the pathology of the disease. In addition, neutralizing IgG anti-GM-CSF antibodies can occur in up to 2–3% of patients treated with rhGM-CSF when it is used to support neutrophil counts after chemotherapy. Interestingly, non-neutralizing IgG anti-GM-CSF were found in 70% of patients vaccinated with rhGM-CSF when it was used as an adjuvant. GM-CSF has also been implicated in the growth of myeloid leukemia cells. We sought to determine whether autoantibodies to GM-CSF were present in patients with AML, CML and MDS based on the hypothesis that these antibodies may contribute to complete remission (CR) and would therefore be present during CR. We studied 38 patients (13 AML, 12 CML, 6 MDS, 1 ALL and 6 CML) for evidence of IgG antibodies to rhGM-CSF (Berlex, Richmond, CA) by ELISA and confirmation by Western blot. IgG anti-rhGM-CSF was detected in 10 patients with myeloid leukemia (3 AML (21%), 3 CML (25%) and 4 MDS patients (67%)), while no antibodies were detected in patients with lymphoid leukemia (p = 0.002), nor in a group of 27 healthy donors (p = 0.001). Antibodies from one patient tested were neutralizing in the TF-1 proliferation assay. Furthermore, Western blotting revealed the presence of IgA and IgM anti-rhGM-CSF in 3 of 20 patients (17%) and in 5 of 20 (25%) patients, respectively, often concurrently with IgG antibodies, suggesting they were derived from unique plasma cells. To our surprise, IgG autoantibodies were present only in patients with active disease, but not in the patients in CR (p = 0.001). Patients studied longitudinally showed an inverse association of IgG titer and disease activity (p < 0.05). We also studied a group of 8 AML patients who received rhGM-CSF to sustain neutrophil counts during chemotherapy and found no difference in the IgG titers between these patients and myeloid leukemia patients that did not receive rhGM-CSF (mean titer = 36.4 RU/ml vs 29.6 RU/ml, respectively). To assess the influence of vaccination with rhGM-CSF, when used as an adjuvant, on the induction of IgG anti-GM-CSF antibodies, we studied 8 patients that received the PR1 peptide vaccine combined with 75 mg rhGM-CSF and incomplete Freund’s adjuvant (Montanide ISA-51) SQ every 3 weeks for 3 total vaccinations. The IgG titers varied inconsistently during the vaccination period, with no significant differences between pre- and post- vaccination titers. We conclude that autoantibodies to GM-CSF are frequent in patients with myeloid leukemia, and they are present in high titer only during active disease. Neither vaccination with rhGM-CSF nor treatment with higher doses of rhGM-CSF influence those titers. Finally, we are the first to show that IgA and IgM autoantibodies are also present in myeloid leukemia patients. These results suggest the possibility that anti-GM-CSF autoantibodies play a role in the pathogenesis of myeloid leukemia.