AN IN-VITRO TEST TO DEMONSTRATE THE INHIBITORY EFFECT OF HOMOLOGOUS IMMUNE SERUM ON THE INFECTIVITY OF COWDRIA-RUMINANTIUM

Homologous immune sheep serum inhibits the infectivity of mice for the Kumm stock of Cowdria ruminantium in an in vitro test. The presence o f 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 oth er heterologous stocks and the Kumm stock. The role played by the humo ral component of the immune response in naturally acquired heartwater is unknown, but probably small compared to the cellular component.