Confocal microscopy assessment of lymphoid tissues with follicular hyperplasia from patients infected with human...

To characterize human immunodeficiency virus (HIV) infection of lymphoid tissues during follicular hyperplasia.

We examined 10 tonsil/adenoid, 3 parotid lymphoepithelial cyst, and 7 lymph node specimens that had been surgically removed from 13 patients infected with HIV-1. Characteristics of productive HIV-1 infection were assessed using immunocytochemistry for HIV-1 p24. Cellular colocalization was determined with the aid of a confocal microscope using double immunofluorescent staining for HIV-1 p24 and cell-specific markers.

All specimens showed follicular hyperplasia. Using confocal microscopy with three-dimensional reconstruction, HIV-1 p24 was seen to be "intimately" colocalized with CD21 within the germinal centers. While lymphoid follicles were generally hyperplastic, only a subset of these follicles contained HIV-1 p24. Occasional HIV-1-expressing mononuclear cells identified outside follicles stained for CD68 or CD3.

The differential involvement of hyperplastic follicles by HIV-1 within individual lymphoid tissues and the intimate colocalization of HIV-1 p24 and CD21 suggest that infected follicular dendritic cells may be an important reservoir of HIV-1 during follicular hyperplasia.