Cationic glycoproteins in sera of patients with acute infections identified as kappa light chain glycosylated IgG

In half of the sera from patients with acute bacterial infections and 15% of the sera from patients with acute viral infections glycoproteins were found that form a scalariform pattern in the cationic range upon isoelectric focusing. The cationic glycoproteins appeared with the clinical illness. After subsidence of the symptoms they disappeared within 4 to 6 weeks. The proteins were identified as immunoglobulin G (IgG) by determination of the NH2-terminal amino acid sequence. Remarkably, these IgG only contained light chains of the kappa type with high proportions of carbohydrates. Both, N-glycosidic- and O-glycosidic-bound glycans were present. The glycosylated light chains may render the cationic IgG multireactive. Thus, it may be part of an early nonspecific immune defense mechanism.