The in vitro response to phytohaemagglutinin during malignant catarrhal fever of rabbits and cattle.

Rabbits with malignant catarrhal fever were recently found to have depressed T and B cell function which was shown by failure of their blood lymphocytes to respond to phytohaemagglutinin (PHA) and other mitogens. In the present work, in contrast, lymphocytes from diseased calves were found to respond well to PHA. Despite using the same source of rabbits and virus as in the earlier study the PHA response of lymph node or peripheral blood cells of rabbits was also found to be normal in most instances but depressed in others; conclusive evidence for hyporesponsiveness due to serum mediated suppression was absent.