Figure 2

CD163 is upregulated in brain of SIV-infected rhesus macaques with and without encephalitis (SIVE). In the frontal white matter (FWM) of seronegative animals, CD163 detection (red) is limited to perivascular MΦs (D). CD163⁺ perivascular MΦs are more frequently observed in SIV-infected animals (E), with substantial perivascular cuffing of CD163⁺ MΦs in those with encephalitis (F). In contrast to seronegative animals, few CD163⁺ cells are seen within the white matter parenchyma of animals with SIV infection but without encephalitis (A). In rare SIV cases, infrequent areas in white matter show CD163⁺ microglia, many appearing to be in an activated state with thickened, retracted processes (B). In SIVE, the number of parenchymal CD163⁺ cells greatly increases and appear to be highly activated (C). Prominent accumulation of CD163⁺ cells is also observed within nodular lesions in SIVE (G). All panels are shown under oil immersion at × 400 magnification. Bioquantification of parenchymal CD163⁺ MΦs/microglia reveals an increase in these cells in FWM of the majority of the animals that developed SIVE, as compared to seronegative and SIV infected animals without encephalitis (H). Data points represent the average percent of parenchymal CD163 expression per animal of immunohistochemical staining in twelve randomly selected 0.31 mm² fields of brain tissue from two seronegative (•), four SIV⁺ (■), and four SIVE (▲) animals. Perivascular cuffs and nodular lesions were excluded from quantification.