Limited CCR5 expression on CD4⁺ T cells in SIV-infected natural hosts. (A) Representative contour plots showing CD4 and CCR5 staining of peripheral blood–derived T cells of chronically SIV-infected SMs, AGMs, mandrills, and sun-tailed monkeys. (B) Summary of CCR5 expression on CD4⁺ T cells from the blood of the species listed in panel A. (C) Representative contour plots showing CD8 and CCR5 staining of T cells isolated from the gastrointestinal tract of chronically SIV-infected SMs and AGMs (left) and the lung (through bronchial alveolar lavage) of an SIV-infected SM (right).