Negative Findings of Leucolysin in the Sera of Cases of Kala-azar

Abstract

Leucopenia is one of the outstanding features in cases of kala-azar. Its pathogenesis is still obscure. By incubating washed leucocytes of the blood of normal individuals with the sera of other normal individuals and of cases of kala-azar, Maggiore and Sindoni 1 found that there was a reduction in number of leucocytes with kala-azar serum, but no reduction with the normal serum. They, therefore, concluded that in the serum of kala-azar cases there was a leucolytic substance,‘leucolysin,’ which is responsible for the occurrence of leucopenia. Their observation was later confirmed by other Italians, 2 , 3 but Teng and Forkner 4 showed that inoculation of killed Leishmania donovani into rabbits failed to produce leucopenia in these animals. In order to confirm or disprove the conclusion of the Italian workers we repeated their experiments and the results are briefly reported below.

Two cc. of blood was withdrawn from the arm vein of a normal individual. After a drop of blood from the tip of the needle was taken, immediately following its withdrawal from the vein, for the initial count of the white blood cells, the blood in the syringe was quickly forced into a 15 cc. centrifuge tube containing 12 cc. of citrated normal saline. The mixture was thoroughly stirred by a glass rod and centrifuged for 3 minutes at medium speed. The supernatant fluid was then removed, fresh citrated saline was added, the mixture again thoroughly stirred, and at the end of the third centrifugation the sediment was made up to its original volume of 2 cc. with citrated normal saline. One cc. of this blood cell suspension in saline was now put into each of 2 small tubes and another white blood cell count was made.