Identification of an acute-phase reactant in murine infections with Trypanosoma brucei.

A 42-kDa protein appeared at a much higher concentration in plasma from Trypanosoma brucei-resistant (C57BL/6) mice after infection than in plasma from trypanosome-susceptible (C3H/He) mice. This protein was purified by sequential steps of gel filtration, protein A-Sepharose affinity chromatography, isoelectric focusing, and ammonium sulfate precipitation. The purified protein was identified as a subunit of the acute-phase reactant haptoglobin. Causes of elevated plasma haptoglobin and its implications for resistance to trypanosomiasis are discussed.