Circulating monocyte subsets in ITP patients are associated with platelet numbers. (A) Representative dot plot of the forward and side scatter in PBMCs showing the gating strategy for analysis of monocyte population. (B) Percent total monocytes based on forward and side scatter gating as a fraction of white blood cells (WBCs) in healthy controls and ITP patients with more > or < 50 × 10⁹/L. (C) Expression of CD14 and CD16 expression in the monocyte population is shown by the representative dot plot, and the gating strategy for analysis of CD16⁺ and CD14^hiCD16⁻ subsets is indicated. Frequencies of CD14^hiCD16⁻ (D) and CD16⁺ (E) subsets in WBCs analyzed by flow cytometry in the same patient and healthy control cohort as in panel B. The absolute numbers in whole blood of total monocytes and CD14^hiCD16⁻ cells (F) as well as CD16⁺ subsets (G) as calculated based on complete blood counts are shown for patients with above and below platelet counts of 50 × 10⁹/L. All P values were calculated using the Mann-Whitney t test. (H) Correlation between absolute CD16⁺ monocyte numbers in ITP patients and their platelet counts as calculated by Spearman correlation test showing a negative association between CD16⁺ monocytes and platelet counts. No significant correlation was seen between the classic CD14^hiCD16⁻ monocytes and platelet counts (see supplemental Figure 2).