Effect of intravenous immunoglobulin on E. coli opsonization in multiple myeloma

Infections are a major source of morbidity in multiple myeloma; E. coli is now the leading pathogen. Intravenous IgG may be a modality which could ameliorate the opsinopathy of multiple myeloma. We infused 6 patients with multiple myeloma with IgG (100 mg/kg) and compared E. coli opsonophagocytosis pre- and post-IgG infusions. Log phase, broth grown E. coli K12 (5 X 10(6)/ml) and normal, dextran-sedimented human neutrophils (5 X 10(6)/ml) were combined in 10% heat inactivated, pre- or post-IgG infusion multiple myeloma serum with 5% agammaglobulinemic serum as a complement source and incubated at 37 degrees C for 30 min. Phagocytosis was quantified as percentage survival of the inoculum. Control survival in heat inactivated normal serum + complement + neutrophils was 1.7 +/- 0.8%. Pre- and post-IgG infusion sera were equally abnormal opsonin sources with 14.3 +/- 6.5% and 17.5 +/- 3.0% survivals. Individually, patients with poor opsonophagocytosis improved with IgG (e.g., pre = 45.2 +/- 3.7%; post = 29.5 +/- 2.3% survival), whereas patients with good opsonophagocytosis showed a deleterious effect (e.g., pre = 2.3 +/- 0.9%; post 23.3 +/- 6.3% survival). To explain these data, we measured deposited IgM and IgG on E. coli by pre- and post-IgG infusion sera in a fluorescence immunoassay. Pre- and post-IgG infusion sera had equally depressed IgM deposition (pre = 13.7 +/- 2.1%; post = 14.5 +/- 2.6% of normal serum), and also equal IgG deposition (pre = 96.8 +/- 6.5%; post = 94.6 +/- 4.8% of normal serum).(ABSTRACT TRUNCATED AT 250 WORDS)