Changes in Leptomonads of Leishmania tropica grown in Media containing Immune Serum

Abstract

THE method for differentiating strains of Leishmania, introduced by Adler^1,2, is to grow them on Locke–serum–agar (semi-solid medium) or on Rugai's medium to which homologous or heterologous immune serum is added. After 3 or 4 days of cultivation, the formation of large irregular, aflagellar cell masses, containing an accumulation of various granules, can be observed. These cell masses were initially considered to be syncytia from which flagellar forms were assumed to re-differentiate at a later stage. Observations made on younger cultures aroused some doubts, however, regarding the nature of these syncytia (personal communication of S. Adler) and we therefore decided to follow up changes produced in the leptomonads by examination of cultures at short intervals, especially during earlier stages of cultivation.