a,b, Transmission electron microscopy images of LPMs from naïve (a) and IL-4c-treated (b) Bhlhe40+/+ and Bhlhe40-/- mice (representative of 2 experiments, n = 2 mice (45–50 images)/group). Scale bar, 2 μm. c-h, Transmission electron microscopy for cellular cross-sectional area (c), endoplasmic reticulum (ER) cross-sectional extent (d), ER luminal width (e), vesicle cross-sectional area (f), nucleoli/cross-section (g), mitochondria/cross-section (h) of LPMs from Bhlhe40+/+ and Bhlhe40-/- mice unstimulated or treated with IL-4c (pooled from 2 experiments, n = 2 mice/group [27–60 cells analyzed, except for 17–20 cells analyzed in (d)]). Data in c-h are mean ± s.e.m; each symbol represents an individual cell (c-h). *P ≤ 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001, unpaired two-sided Student’s t -test.