T cell-dependent elimination of dividingTrypanosoma grosifrom the bloodstream of Mongolian jirds

Abstract

Mongolian jirds,Meriones unguiculatus, are susceptible to infection withTrypanosoma grosi, which naturally parasitizesApodemusspp. The present study investigated T cell dependence of elimination ofT. grosifrom the bloodstream of jirds byin vivoT cell depletion using a monoclonal antibody (HUSM-M.g.15). In T cell-depleted jirds, elimination ofT. grosi, particularly the dividing forms, from the bloodstream was significantly delayed, occurring at around week 3 p.i. The kinetics of serum levels of IgM and IgG specific to trypanosomes in T cell-depleted and control immunocompetent jirds were different; peak levels of IgM were noted on days 6–8 p.i. around the time of peak parasitaemia (day 6 p.i.) in immunocompetent jirds, whereas the serum levels began to increase abruptly after day 10 p.i., peaking at around day 18 p.i. in T cell-depleted jirds. Similarly, serum IgG increased after day 6 p.i. in immunocompetent jirds, in contrast to after day 12 p.i. in T cell-depleted jirds, and the level increased steadily even after disappearance of parasitaemia. Our findings indicate that T cells play a major role at least in the ‘first crisis’ during elimination of dividingT. grosifrom the bloodstream.