Naïve CD8 T cell RNA sequencing in C57BL/6 and MD4 mice

The presence of B cells is essential for the formation of CD8 T cell memory after infection and vaccination. In this study, we investigated whether B cells influence the programming of naïve CD8 T cells prior to their involvement in an immune response. RNA sequencing indicated that B cells are necessary for sustaining the FOXO1-controlled transcriptional program, which is critical for their homeostasis. Without an appropriate B cell repertoire, mouse naïve CD8 T cells exhibit a terminal, effector-skewed phenotype, which significantly impacts their response to vaccination. A similar effector-skewed phenotype with reduced FOXO1 expression was observed in naïve CD8 T cells from human patients undergoing B cell-depleting therapies. Furthermore, we show that patients without B cells have a defect in generating long-lived CD8 T cell memory following COVID vaccination. In summary, we demonstrate that B cells promote the quiescence of naïve CD8 T cells, poising them to become memory cells upon vaccination. The spleens of 5 x 10-week-old female wildtype C57BL/6J mice and 5 x 10-week-old female hemizygous MD4 transgenic mice (originally made on a C57BL/6J background) were harvested and enriched for CD8 T cells using a mangetic enrichment kit (BioLegend). Cells were then stained and sorted using a FACS Aria (BD Biosciences) cell sorter , gating on CD3+CD8+B220−CD44low live single cells.