Activation of Th1 or Th2 cells is associated with production of specific
immunoglobulin isotypes, offering the opportunity to use antibody measurement for evaluation of T cell function.
Schistosomiasis and
visceral leishmaniasis are diseases associated with Th2 activation. However, an
IgE response is not always detected in these patients. In the present study we evaluated specific
IgE antibodies to S. mansoni and L. chagasi
antigens by ELISA after depletion of serum
IgG with
protein G immobilized on
Sepharose beads or RF-absorbent (purified sheep
IgG antibodies anti-human
IgG). In
schistosomiasis patients, specific
IgE to SWAP
antigen was demonstrable in only 10 of 21 patients (48%) (mean absorbance +/- SD = 0.102 +/- 0.195) when unabsorbed serum was used. Depletion of
IgG with
protein G increased the number of specific
IgE-positive tests to 13 (62%) and the use of RF-absorbent increased the number of positive results to 20 (95%) (mean absorbances +/- SD = 0.303 +/- 0. 455 and 0.374 +/- 0.477, respectively). Specific
IgE anti-L. chagasi
antibodies were not detected in unabsorbed serum from
visceral leishmaniasis patients. When
IgG was depleted with
protein G,
IgE antibodies were detected in only 3 (11%) of 27 patients, and the use of RF-absorbent permitted the detection of this isotype in all 27
visceral leishmaniasis sera tested (mean absorbance +/- SD = 0.104 +/- 0.03). These data show that the presence of
IgG antibodies may prevent the detection of a specific
IgE response in these parasite diseases. RF-absorbent, a
reagent that blocks
IgG-binding sites and also removes
rheumatoid factor, was more efficient than
protein G for the demonstration of specific
IgE antibodies.