BV2 microglia in three-dimensional (3D) collagen gels shift as a population to express CD40 in response to lipopolysaccharide (LPS) stimulation. BV2 microglia in monolayer, coated monolayer and 3D culture conditions were activated with 1 μg/ml LPS (+LPS) and CD40 expression analysed with flow cytometry at 24 hrs. (A) Histograms show percentage of CD40+ cells. Data are mean ± SD from three independent experiments. **P < .01, ****P < .001; one-tailed Mann-Whitney U test. (B) Histograms show median fluorescence intensity (MFI) of CD40+. Data are mean ± SD from three independent experiments. *P < .05, **P < .01 ; Kruskal Wallis with Dunn’s Multiple Comparison test.