Use of patients' sera for immunoperoxidase demonstration of infectious agents in paraffin sections

Using patients' sera diluted from 1:10 to 1:1,000 as the primary antibodies in indirect immunoperoxidase staining, the authors visualized a variety of infectious agents in formalin-fixed, paraffin-embedded tissue sections. The target lesions included 1) pyoderma caused by Staphylococcus aureus, 2) cryptococcal infection, 3) dermal sporotrichosis, 4) colon ulcer caused by amebic dysentery, 5) cutaneous leishmaniasis, and 6) chronic liver abscess containing ova of Ascaris lumbricoides. The infectious agents were clearly identified in the respective lesions. Paraffin sections of other kinds of infectious lesions served as controls to clarify the specificity of the immunostaining. While the sera of patients with bacterial and fungal infection showed a wide range of cross-reactivity against bacteria and/or fungi, those with parasitic infection exhibited a relatively good specificity for the pathogen. Almost no immunoreactivity of endogenous human IgG in the paraffin sections was demonstrated under the conditions of this study. This approach can be used in diagnostic pathology, particularly when specific heteroantisera or monoclonal antibodies are unavailable.