In vitro proliferative response of spleen cells is not influenced by gut microbiota or LPS-rich sterile diet. Spleen cells isolated from CV mice and GF mice fed either diet were stained with CFSE fluorescein and stimulated with ConA. After 72 h the cells were analyzed by FACS. Histograms in this figure show the CFSE staining profile of lymphocytes negative for CD19 antigen (B cell marker). Proliferation was measured as the percentage of cells showing decreased staining intensity of CFSE compared to the intensity of the CFSEbright population. Open histograms represent unstimulated control cells. The presented data are from a representative experiment. Each experiment was repeated at least three times with similar results.