Serum immunoglobulin concentrations of cattle in a herd with bovine leukosis.

Consistent relationship was not found between the serum concentrations of immunoglobulin IgM and IgG and the concentration of blood lymphocytes (Bendixen index) in 289 Holstein-Friesian heifers and cows from a dairy herd in which bovine lymphoma had been identified repeatedly. Serum IgM was present in all cattle, and those cows with highest concentrations of blood lymphocytes generally had higher levels of IgM.