3 - Immunohistology of Infectious Disease

Abstract

Pathologists play an important role in the diagnosis or exclusion of infectious diseases. Traditionally, the diagnosis of infectious diseases relies on serologic assays and cultures. Serologic results may be difficult to interpret in the setting of immunosuppression, fresh tissue is not always available for culture, and culture of fastidious pathogens can be difficult and may take weeks or months to yield a result. Although some microorganisms or their cytopathic effects may be readily identifiable on routine and/or histochemical stains, often these changes are not specific, or are sparse in the sample evaluated. Immunohistochemistry and molecular diagnostic techniques have proven to be useful tools in the diagnosis of infectious disease in tissue samples. These techniques are especially useful in the identification of microorganisms that are present in low numbers, stain poorly, are fastidious to grow, are non-cultivable, or exhibit an atypical morphology. It is important to remember that there may be widespread occurrence of common antigens among bacteria and pathogenic fungi, and both monoclonal and polyclonal antibodies must be tested and validated for possible cross-reactivity with other organisms.