Immunophenotyping and assessment of cell function by three-color flow cytometry of peripheral blood lymphocytes

Infection by the human immunodeficiency virus type 1 (HIV-1) is known to cause a number of changes in the immunophenotypic profile of patients even in the early asymptomatic stages of disease. Such "surrogate markers" are known to correlate with the stage of HIV disease and often are predictive of outcomes. The best known of these is the absolute count of T helper lymphocytes, or CD4 cells, which undergoes a gradual decline as the virus infects greater and greater numbers of these cells (1). A number of other markers have been found, some of which also are predictive of outcome in many cases. These include prevalence and intensity of the CD38 marker on CD8 T cells, percentage of CD4 cells exhibiting loss of the CD26 and CD28 markers, and percentage of CD4 cells with the CD95 marker (2). The CD38 intensity of CD3/CD8 cells has, in fact, been more closely correlated with future disease progression in patients than the CD4 count (3). The following method is a comprehensive immunophenotyping panel that incorporates all of these markers and provides several parameters by which to monitor disease progression and advise clinicians on treatment options.