Detection of specific IgE antibodies in parasite diseases

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.