[Determination of human IgG subclass by EIA]

The human IgG subclasses have specific characteristics in response to respective antigens, and determination of their characteristics is important in analysis of infectious, autoimmune and other diseases. We developed quantitative EIA (ELISA) assays for Japanese human IgG subclasses with excellent reproducibilities using monoclonal antibodies. The assays enable determinations between 0.4 ng/ml and 2,000 ng/ml. The serum IgG subclass levels (mean+SD) in healthy adults are as follows: IgG1, 5.93 + 2.07 mg/ml (59.94%); IgG2, 3.36 + 1.84 mg/ml (32.97%); IgG3, 0.30 + 0.19 mg/ml (3.07%); and IgG4, 0.22 + 0.15 mg/ml (2.34%). Excellent correlation was obtained between total IgG level measured by EIA using anti-whole human serum and the sum of the four IgG subclasses (IgG1+IgG2+IgG3+IgG4). Samples from every patient with M protein of IgG1 and IgG2 types shown by M band on immunoelectrophoresis also had the highest level in four IgG subclasses.