The Number of CD1a + Large Low-Density Cells with Dendritic Cell Features Is Increased in the Peripheral Blood of HIV + Patients

Abstract

Employing a discontinuous Percoll gradient following Ficoll-Hypaque separation of peripheral blood mononuclear cells from normal subjects ( n = 14) and patients with HIV-1 infection ( n = 50), we separated a population of low-density cells consisting of monocytoid cells, lymphocytes, and some granulocytes. In cytospin preparations, less than 5% of the monocytoid cells were positive for nonspecific esterase and CD14. However, CD1a was positive in 5-20% of these cells. Ultrastructurally, CD1a-labeled immunogold particles were demonstrated on the monocytoid cells which bore some features of dendritic cells. Flow cytometry of the low-density cells identified a subset of buoyant, large cell population, which excluded lymphocytes. This large low-density cell (LLDC) population was significantly expanded in patients with HIV infection and comprised 32.3 ± 21.3% of low-density cells compared to 7.0 ± 2.8% in normal subjects ( P < 0.0001). Of the LLDC population 45.2 ± 23.4% were CD1a + in patients compared to 17.5 ± 13.3% in normal subjects ( P ≤ 0.0001). HLA-DR and HLA-DQ were coexpressed in approximately 70 and 50% of these CD1a + LLDC, respectively. A simple nonculture assay method employed by us facilitates rapid screening of infected blood specimens for the CDla + large low-density cells with dendritic cell features, which could be an additional parameter to monitor HIV disease progression.