Human immunodeficiency virus-rich multinucleated giant cells in the colon: a case report with transmission electron microscopy, immunohistochemistry, and in situ hybridization.

Multinucleated giant cells (MNGCs) expressing the human immunodeficiency virus (HIV) are characteristically found in hyperplastic tonsils and adenoids, acquired immunodeficiency syndrome encephalitis, vacuolar myelopathy, and lymph nodes coinfected with opportunistic pathogens. We identified similar polykaryons in the hyperplastic gut-associated immune system of an HIV-infected patient. Colonic biopsy specimens from this patient with heme-positive stools were studied by light and transmission electron microscopy (TEM), immunohistochemistry, and in situ hybridization for HIV-specific RNA. No bleeding source was identified by endoscopic or light microscopic examination of the biopsied tissues. There was diffuse and nodular lymphoid hyperplasia with germinal centers. HIV RNA-positive and p24 gag-positive Langhans'-type MNGCs and mononuclear cells (MNCs) were present within the lamina propria The MNGCs and MNCs were identified as macrophages on the basis of TEM and expression of CD68, HAM56, and lysozyme markers. They also expressed S100 protein, a marker of dendritic/Langerhans' cells, but they lacked Birbeck granules by TEM. In situ hybridization demonstrated RNA expression by MNGCs, MNCs, and follicular dendritic cells. TEM revealed budding and mature HIV particles on the plasma membranes of MNGCs, MNCs, and follicular dendritic cells. We conclude, therefore, that hyperplastic gut-associated immune systems can contain HIV-positive MNGCs and MNCs of the type seen in tonsils and adenoids and opportunistic pathogen-infected lymph nodes. Associated with immune activation, macrophages can express markers of dendritic/Langerhans' cells, cell types derived from the same CD34-positive bone marrow progenitor.