Abstract
Leucopenia is one of the outstanding features in kala-azar. It develops early in the course of the disease and is frequently out of proportion to the anemia. This fact has been well recognized, and its diagnostic value repeatedly emphasized. The mechanism of the development of this phenomenon is, however, by no means understood. By incubating leucocytes with blood serum, Maggiore and Sindoni 1 claimed to have demonstrated the presence in the blood serum of patients with visceral leishmaniasis, of a substance which is leucocytolytic. Arena 2 confirmed this finding. Their results were not at all conclusive, and there has been no further confirmation. Some workers 3 , 4 believed that leucopenia as well as anemia in this disease is myelophthisic, the overgrowth of the macrophages (“clasmatocyte tissue”) being comparable to the metastatic growths of carcinoma in blood-forming organs. This does not explain satisfactorily the early appearance of leucopenia when the infection is only beginning and the “crowding out” of the myeloid tissue hardly can have taken place.
It has been suggested, 5 , 6 , 7 in discussing the problem of leucopenia in general, that there are possibly 2 factors concerned in the maintenance of a normal level of leucocytes in the peripheral blood, viz., a maturation factor and a chemotatic factor. Whether or not such factors also operate in the production of leucopenia in kala-azar, one can only conjecture. Forkner and Zia 8 have shown that pentose-nucleotide, which was considered by Doan 5 as an example of a chemotatic substance for leucocytes, did not produce any significant change in the number of leucocytes when administered intramuscularly to patients with kala-azar. One may further postulate that there may be present in this disease an unknown factor which has a depressive effect on the myeloid tissue. The fact that the leucopenia and anemia begin to improve quite steadily soon after the institution of specific treatment may suggest the actual presence of some such factor which can be removed or counteracted by controlling the infection. It seems, therefore, worthwhile to investigate whether such a factor is present in the body of Leishmania donovani or its metabolites. It occurred to us that, by inoculation into animals of the killed organisms or their metabolites, it might be possible to bring about in the blood a picture comparable to that produced by actual infection.
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