Lymphocytes from patients cured of
amebic liver abscesses proliferate and produce
gamma interferon upon incubation with soluble Entamoeba histolytica
antigen: however,
amebic liver abscesses exhibit a relentless progression without treatment. To determine whether suppressive factors are present in sera, we studied T-lymphocyte responses to total soluble E. histolytica
antigen by using cells from five patients treated for
amebic liver abscesses in the presence of 15 different
immune sera and 10 control sera. In the presence of
immune sera, E. histolytica
antigen-induced lymphocyte proliferation decreased by 63% and production of
gamma interferon was reduced by 93.2% (P less than 0.01).
Immune sera had no effect on the mitogenic responses of patient lymphocytes to
phytohemagglutinin or on the proliferative responses of control lymphocytes to
phytohemagglutinin or
tetanus toxoid. The suppressive activity of
immune sera diminished as the time between
therapy for
amebic liver abscesses and serum collection increased (P less than 0.05). Suppressive activity did not correlate with the titers of serum anti-amebic antibody and was not affected when serum was absorbed with viable amebic trophozoites. In conclusion, soluble factors present in the sera of
amebic liver abscess patients suppressed in vitro lymphocyte responses to E. histolytica
antigen and may have contributed to the lack of development of effective in vivo cell-mediated immune responses following the onset of
amebic liver abscesses.