Quantitative studies on bovine immunoglobulins, normal plasma levels of IgG2, IgG1, IgM and IgA.

Using monospecific sheep antisera, the mean plasma immunoglobulin concentrations in 82 Ayrshire milking cows were found, by the single radial diffusion method, to be: IgG2 10-91 plus or minus 4-30, IgG1 9-76 plus or minus 2-59 and IgM 2-71 plus or minus 1-22 mg/ml (plus or minus SD). IgA levels in the same group of 82 cows were determined by a simple, sensitive coated tube radioimmunoassay and had a mean value of 0-32 plus or minus 0-16 mg/ml. The frequency distributions of IgG1, IgM and IgA were approximately log normal, whereas that of IgG2 was bimodal with two populations with means of approximately 7 and 14 mg/ml. An 18-fold difference was found between high and low IgG2 levels whereas only three- to four-fold differences were recorded for IgG1 levels in the same population. Eight-fold differences were found for IgM and IgA levels. The effect of age (2-9 years) on sampling could be disregarded for IgG1, IgG, IgM and IgA levels, but cows above 6 years of age had significantly higher IgG2 levels.