Donor binding variability does not correlate with a specific cell subset within PBMC. Donor PBMC were stained with anti-CD4-FITC, anti-CD8-FITC, anti-CD14-FITC, or anti-CD20-FITC and the percentage of each subset measured by flow cytometry. PBMC from donors were also incubated with 2000 pg of p24 (HIVTH), and cell-bound virus was measured by ELISA as before. HIV binding variability is plotted on the y-axis and percentage marker positive cell subsets is plotted on the x-axis. r2 represents the goodness of fit value. Data represent means ± SD of triplicate determinations.