Male and female C57BL/6 mice were exposed to cSiO2 (1 mg), MWCNTs (50μg), or dispersion media (DM) vehicle control (50 μl), once per week for 4 weeks and harvested 8 weeks after the last exposure. Whole lung tissue was digested and used for flow cytometry to identify immune cell populations (A) and cell surface marker expression as determined by median fluorescence intensity (MFI) (B). Cell population frequencies expressed as a percentage of CD45+ cells within the lung tissue; data represented as mean ± SEM, n = 4–5. * p < .05, ** p < .01, *** p < .001, **** p < .0001 compared to same-sex DM control, # compared to males of the same treatment. IM/Mo, interstitial macrophage/monocytes.