Impact of oral Bacillus Calmette–Guérin on B220 receptor expression in Peyer's patches of lactating mice: Analysis of receptor percentiles and cell frequencies

The oral administration of the Bacillus Calmette-Guérin (BCG) vaccine aims to replicate the earliest inoculation route. We investigated the impact of this method by analyzing major Peyer's Patches (PP) cell lineages in mice. Oral BCG altered T/CD3, B/B220, double-labeled CD3-B220, double-labeled IgMB220, and triple-labeled CD49b-CD3-B220 cells. Both immunized (IL) and non-immunized (NIL) lactating mice served as controls in the flow cytometry analyses. The findings suggest that oral BCG vaccination induces changes in specific cell lineages, which may have implications for the development of novel vaccination strategies. Since population percentages vary according to source, frequencies based on fluorescence intensity were calculated according to percentiles, and subpopulations were subsequently analyzed per percentile. A robust statistical analysis assessed whether immunization influenced either the percentage of B220-labeled cells or the cellular expression of B220 per bin. The Thy1.2-depleted population revealed B220 as a receptor shared by both B and T lymphocytes. Statistical evaluation by receptor type and cell difference distance revealed subpopulations in transitional phases and showed that, among polychromatic receptor cells such as B220-IgM (CD11b^-), oral BCG selectively increased B220 expression. Oral BCG also induced CD3 cell activation, evidenced by a decrease in CD5 within the double-labeled CD3-CD5 cluster, despite an overall increase in CD3 receptors. Receptor analysis in regularly turning-over populations, such as PP lymphoid tissue, highlighted the double-labeled B220-CD3 cells. Notably, oral BCG influenced the development of double-labeled B220-CD3 cells in NKT-like populations.