Abstract:
Homologous immune sheep serum inhibits the infectivity of mice for the Kumm stock of Cowdria
ruminantium in an in vitro test. The presence of complement and an optimal ratio between the reagents
are of cardinal importance. With the exception of the Ball 3 stock, there is no cross-inhibition between
the immune sera of sheep infected with several other heterologous stocks and the Kumm stock. The
role played by the humoral component of the immune response in naturally acquired heartwater is
unknown, but probably small compared to the cellular component.
