Activation of Th1 or Th2 cells is associated with production of specific im
munoglobulin isotypes, offering the opportunity to use antibody measurement
for evaluation of T cell function. Schistosomiasis and visceral leishmania
sis are diseases associated with Th2 activation. However, an IgE response i
s not always detected in these patients. In the present study we evaluated
specific IgE antibodies to S. mansoni and L. chagasi antigens by ELISA afte
r depletion of serum IgG with protein G immobilized on Sepharose beads or R
F-absorbent (purified sheep IgG antibodies anti-human IgG). In schistosomia
sis patients, specific IgE to SWAP antigen was demonstrable in only 10 of 2
1 patients (48%) (mean absorbance +/- SD = 0.102 +/- 0.195) when unabsorbed
serum was used. Depletion of IgG with protein G increased the number of sp
ecific IgE-positive tests to 13 (62%) and the use of RF-absorbent increased
the number of positive results to 20 (95%) (mean absorbances +/- SD = 0.30
3 +/- 0.455 and 0.374 +/- 0.477, respectively). Specific IgE anti-L. chagas
i antibodies were not detected in unabsorbed serum from visceral leishmania
sis patients. When IgG was depleted with protein G, IgE antibodies were det
ected 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 presen
ce of IgG antibodies may prevent the detection of a specific IgE response i
n 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.