Haptoglobin levels in serum of various strains of mice.

Only a single type of haptoglobin was found in the serum of 11 strains of mice, but there were wide variations between strains with respect to the amount of haptoglobin found. In the AKR and C3H strains, in which haptoglobin was low or absent, various agents stimulated production of high levels of haptoglobin. Serum haptoglobin rose in association with the development of leukemia in AKR mice, but remained low when C3H mice developed mammary tumors.