1. distinctive structures frequently formed in the nucleus or cytoplasm (occasionally in both locations) in cells infected with certain filtrable viruses; may be demonstrated by means of various stains, especially Mann eosin methylene blue or Giemsa techniques and visible by light microscopy. Nuclear inclusion bodies are usually acidophilic and are of two morphologic types: 1) granular, hyaline, or amorphous bodies of various sizes, Cowdry type A inclusion bodies, occurring in such diseases as herpes simplex infection or yellow fever; 2) more circumscribed bodies, frequently with several in the same nucleus (and no reaction in adjacent tissue), the type B bodies, occurring in such diseases as Rift Valley fever and poliomyelitis. Cytoplasmic inclusion bodies may be: 1) acidophilic, relatively large, spheric or ovoid, and somewhat granular, as in variola or vaccinia, rabies, and molluscum contagiosum; 2) basophilic, relatively large, complex combinations of viral and cellular material, as in trachoma, psittacosis, and lymphogranuloma venereum. In some instances, inclusion bodies are known to be infective and probably represent aggregates of virus particles in combination with cellular material, whereas others are apparently not infective and may represent only abnormal products formed by the cell in response to injury.
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