Amoebic liver abscess--serum anticomplementary screening for immune complexes

Suppression of T-lymphocyte responses to Entamoeba histolytica antigen by immune sera

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.

Specific circulating immune complexes in amoebic liver abscess

A micro enzyme-linked immunosorbent assay was used to detect the presence of amoebic antigen in polyethylene-glycol-precipitated circulating immune complexes (CIC). A cutoff dilution of greater than 1:160 for the precipitates was taken to be of clinical significance. Among the patients with amoebic liver abscess, 93% (14 of 15 confirmed cases) had indications of amoebic antigen in CIC. In 57% of the suspected cases of amoebic liver abscess, amoebic antigen could be detected in CIC. The specificity of the technique for the demonstration of specific amoebic antigen is indicated by the undetectable levels of amoebic antigen in CIC in serum samples from nine cases of nonamoebic hepatic diseases and 10 apparently healthy subjects. It is thus believed that the specific diagnosis of an individual case of amoebic liver abscess can be made by demonstrating specific amoebic antigen in CIC.

Amoebic liver abscess: serum immunoglobulins and complement in Northern Nigerian patients

Immunoglobulins (IgG, IgA, IgM and IgD) and complement components of both the classical and alternative pathways (C1q, C3 and C4, and factor B) were measured in the sera of 15 Nigerian patients with proven amoebic liver abscess and compared with 30 age-matched controls. IgA, C3 and factor B were significantly higher in amoebic liver abscess patients. The differences in IgG, IgM, IgD, C1q and C4 levels between patients and controls were not significant.