Tumor stage-specific macrophage repolarization in the myeloma niche in the absence of Tpl2. Macrophage polarization was assessed using flow cytometric analysis of C11b⁺/F4/80⁺ macrophages from BMs of age-matched (8-month old) and “tumor matched” wild-type (Vκ*MYC/Tpl2^+/+) and Vκ*MYC/Tpl2^−/− animals. Representative results from 3 animals in each group are shown. The C11b⁺/F4/80⁺ gate is shown to the left. The dot plots represent the frequency of the M1-like fraction (CD68^int/Ly6C^int) and M2-like fraction (CD68^hi/Ly6C^hi) in the total C11b⁺/F4/80⁺ gate in each genotype. M1 polarization has been shown to result in downregulation of CD68 in macrophages.⁷⁶  On the right panels, histograms depict the relative frequency of iNOS⁺ and Arginase-1⁺ cells in each subpopulation, depicted in RED (M1-like) and BLUE (M2-like). APC, allophycocyanin; FITC, fluorescein isothiocyanate; PE, phycoerythrin.