GT induces preferential death of monocytes. Incubation of PBMCs with GT resulted in a substantial decrease in the frequency of viable monocytes during the stimulation period and an increase in the lymphocyte-monocyte ratio. Panel A demonstrates GT-induced loss of monocytes by scatter. In the example shown, after 6 hours of incubation with 35 ng/mL GT, the lymphocyte fraction was 47.4%, while the monocyte fraction was 1.24% of the gated PBMC population. Panel B represents the control sample, in which monocytes amount to 16.2% of gated events, while the lymphocyte fraction was 49.8%. Panel C displays a similar loss of monocytes following incubation with an AF lysate. Following incubation for 6 hours with 32 μLAF lysate, the lymphocyte fraction was 20.3%, while the monocyte fraction was 2.4%. Panel D represents the control sample. Unstimulated cells show typical lymphocyte and monocyte fractions within the PBMC population, 28.6% and 11.4%, respectively. The ratio of lymphocytes to monocytes increased with escalating doses of GT. Panel E illustrates that the preferential loss of monocytes leads to an increasing lymphocyte-monocyte ratio in the presence of GT. Unstimulated PBMCs displayed a lymphocyte (□)–monocyte (▪) ratio of 2.8:1. This ratio increased to 13:1 for cells incubated with GT 150 ng/mL and 42:1 when PBMCs were incubated with GT 300 ng/mL. By linear regression (not shown) a strong positive correlation was seen between increasing GT concentration and lymphocyte-monocyte ratio (r² = 0.91, P < .001). Arrows indicate location of monocytes by scatter. Error bars indicate SEM.