Circulating antibodies and antigenic cross-reactivity in Hendersonula toruloidea and Scytalidium hyalinum infections

SUMMARY Twelve (34%) of thirty‐five patients with an active infection on the palms or soles caused by Hendersonula toruloidea or Scytalidium hyalinum were found to have circulating antibodies to these organisms by counter immunoelectrophoresis or immunodiffusion, compared with 9% of uninfected controls. In every instance there was cross‐reactivity between the positive patients' sera and the heterologous non‐dermatophyte antigen. Using crossed and intermediate gel immunoelectrophoresis it was found that cytoplasmic extracts of H. toruloidea and S. hyalinum showed 34 and 41 precipitin peaks respectively, most of which were shared by both organisms. No cross‐reactions were observed between the nondermatophyte cytoplasmic extracts and hyperimmune animal antisera raised to Trichophyton rubrum, Trichophyton interdigitale, Aspergillus fumigatus or Candida albicans. Exoantigens prepared from the two non‐dermatophytes showed similar cross‐reactivity between the two species. It appears that H. toruloidea and S. hyalinum are very similar in antigenic structure, a finding which lends support to the view that they may be closely related. They are also antigenically distinct from other pathogenic fungi which commonly infect skin, a fact which may be useful in their cultural identification as well as their recognition in tissue specimens.