Mean values (± standard error and 1.96 standard error) of Tregs in subjects with PMF according to genotype. The difference among Tregs in PMF genotypes was significant (Kruskal-Wallis analysis of variance, P = .05). Treg frequency in persons with a JAK2V617F genotype (N = 126; median, 1.33%; range, 0% to 10.2%) was higher than in subjects with a JAK2 wild-type genotype (N = 74; median, 0.98%; range, 0% to 6.69%; P = .002) and subjects with a CALR mutation genotype (N = 50; median, 1.05%; range 0% to 6.69%; P = .06). Subjects with a JAK2V617F genotype and a ≥50% allele burden had a higher frequency of Tregs than subjects with <50% allele burden (median, 1.50%, range, 0% to 10.2% vs 1.24%, range, 0.01% to 6.11%; P = .07). Subjects with a MPL mutation genotype (N = 9) or no detectable mutation (triple negative) (N = 16) were not included in the comparisons of Treg frequency between PMF genotypes.