Trophoblast cells modify B-cell phenotype. Purified B cells (105 cells/100 μL medium) were cultured in normal medium (M), trophoblast-conditioned medium (TB-CM), or directly co-cultured with trophoblast (TB) cells. After 48 h, recovered B cells were stained with B cell lineage surface markers CD19, CD24, CD27, CD38, and IgM to discriminate between the Breg, transitional, IgM-memory, and plasmablast subpopulations. Representative flow cytometry panels indicating gating strategy shown in (A), with combined results from three independent experiments performed in duplicate shown in (B). *P < .05, **P < .01, ***P < .001