MPD development relies on the presence of CD4 T cells. (A-D) MHCII^KO mice were assessed by flow cytometry. WT and CD11c^ΔMHCII mice are shown for comparative purposes. (A) Spleen weight and (B) percentage of peripheral mononuclear neutrophils (PMN) (CD11b^highGr1⁺) among total splenocytes at 12 weeks (n = 11, 13, 6), 30 weeks (n = 22, 16, 3), and 1 year (n = 23, 25, 4) of age. (C) Absolute number of PMN among total splenocytes at 12 weeks (n = 11, 13, 6), 30 weeks (n = 18, 11, 3), and 1 year (n = 22, 23, 4) of age. (D) Absolute number of myeloid precursor-like cells among total splenocytes at 12 weeks (n = 9, 11, 6), 30 weeks (n = 12, 7, 3), and 1 year (n = 22, 23, 4) of age. Mean ± standard error of the mean and individual data points are shown. (E) Naive (CD25⁻CD62L⁺CD44⁻) and memory (CD25⁻CD44⁺) CD4 cells from 6 mice were sorted, and qPCR for Flt3L was performed. Mean ± standard error of the mean are shown. The P values were determined using an unpaired t test.