The Effect of Homologous Rabbit Antiserum on the Growth of Leishmania tarentolae—a Fine Structure Study

SYNOPSIS. The fine structure of Leishmania tarentolae growing in the presence of homologous rabbit antiserum was investigated. Immediately after agglutination of the promastigotes, a dense band between pellicles of adjacent cells could be seen, and a surface coat was rendered visible. The cells did not fuse. At dilutions of antiserum from 1:100–1:1200 the promastigotes continued to grow, forming large masses. By 5 days these consisted of individual cells adhering to one another. In cross-section, any 2 cells were separated by 2 membranes with associated subpellicular fibrils and a dense band between the 2 membranes. The term syncytium generally refers to a multinucleate cell originating by fusion of several cells and has been used to mean a multinucleate cell arising from nuclear division unaccompanied by cytokinesis. Therefore, it is unlikely that the masses formed in the presence of homologous antiserum are syncytia.