The present observations on the kinetics of Cathepsin II extracted from the organs of normal animals strikingly parallel the observations of Lurie. He has previously shown that during the course of a primary blood-stream infection of normal rabbits with tubercle bacilli, the latter are more effectively destroyed in the spleen and liver than in the kidneys and lungs. Our data indicate that the speed with which the enzymes of the first two organs hydrolyze benzoyl-l-arginineamide (BAA) is much greater than that of the latter. The rank order of activity is: spleen τ; liver τ; kidney τ; lung.

The heightened physiological activity and the accelerated local inflammation observed by Lurie as a result of reinfection with virulent tubercle bacilli was accompanied in our experiments by an accelerated rate of activity of Cathepsin II from spleens, lungs, and kidneys. Immunization of rabbits with an avirulent strain of tubercle bacilli did not increase the speed of hydrolysis by endocellular proteinases, just as it failed to increase the specific phagocytic capacity of the cells for tubercle bacilli in Lurie's experiments.

1

A preliminary report on this work appeared in Federation Proc., 2, 96, 1943.

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