Specific IgE responses in human strongyloidiasis.

IgE antibodies directed against Strongyloides stercoralis larval antigens were measured by a newly developed radioallergosorbant test (RAST). One hundred and fifty-two samples of sera from patients with parasitologically proven S. stercoralis infection were tested. One hundred and thirty-six of these (89.5%) were positive for parasite-specific IgE. Of 50 presumably non-infected North American adult control sera, 49 (98%) were negative. All sera from patients with other parasites were negative, except for two sera from subjects with Ascaris lumbricoides, who exhibited low positivity. Of eight sera from non-infected patients with allergies and high IgE levels, one was weakly positive, and the other seven were negative. Considerable individual variability was present in the levels of specific IgE as measured by the RAST in the infected patients. Significant differences were also found among the three major demographic groups which composed our study population, with Asians having higher values than Latin Americans and the latter having higher values than North American patients. We conclude that the majority of patients with strongyloidiasis develop IgE antibodies directed against antigens from filariform larvae, the invasive form of the parasite. While the functional significance of this response remains to be defined, the RAST for IgE may be a useful adjunct in the immunological evaluation of these patients.