Retroviral analysis of the in vivo–differentiated MCs/basophils in the blood of patients with AIDS.

In the depicted experiment, the cells in the peripheral blood of a patient with both AIDS and asthma were stained with anti-HIV-1 p24 IgG (brown) followed by anti-tryptase IgG (pink) (A). Similar tryptase⁺/p24⁺ MCs/basophils were found in the blood of 5 other patients with AIDS. In the negative control experiments, immunoreactive p24 was not detected in the tryptase⁺ MCs/basophils present in 3 asthma patients that were not infected with HIV-1 (data not shown). Because the immunohistochemical data indicated the presence of viral protein, electron microscopy was carried out to evaluate whether or not the MCs/basophils in 2 of these patients contain intact retrovirus (B). The open and closed arrows in the depicted electron micrograph indicate secretory granules and intact retrovirus, respectively, in these MCs/basophils. N refers to the nucleus. Although certain populations of human eosinophils are susceptible to HIV-1 ex vivo,59 the depicted HIV-1–infected cell clearly is not an eosinophil, T cell, or macrophage based on its ultrastructure.