Figure 8. Histone 1 upregulates MHC class II expression in microglia.

( a) Primary microglial cultures were incubated in serum-free medium for 24 hrs and identified with Iba1 (red). ( b) Cultures were then treated with histone H1 (100 nM) for 24 hrs. Activated microglia were identified with OX-6 (which labels MHC-class II, green) so that double-stained cells appear yellow. Scale bars: 100 μm. ( c) Histone H1 dose-dependently increased the expression of MHC class II to a level similar to that elicited by LPS (1 μg/ml). 25 nM H1 produced a 6-fold increase in expression of OX-6 (p<0.001) while the effects of 50 nM histone H1 were not different from the maximal response to LPS at 1 μg/ml. Error bars represent ± SEM for all conditions, one-way ANOVA, Bonferroni post-hoc correction.