A Study of Cytoplasmic Inclusions in Trypanosoma lewisi and their Relationship to the Formation of Antibody

SUMMARY: Developmental forms of Trypanosoma lewisi continue to increase in number when the ‘crisis’ (normally occurring at the 10th day) is inhibited; the inclusions which they contain also increase in number, density and refraetile power. Suspensions of killed developmental forms containing multiple inclusions have greater protective power against a challenge infection than have similar suspensions of adult forms which contain a single inclusion. It is suggested that the multiple inclusions contain an antigenic factor which stimulates the production of a trypanocidal antibody and reacts with it to produce the crisis, but the single inclusions of the adult forms which survive the crisis have different antigenic properties.