Peripheral blood was collected from six SPF White Leghorn hens, randomly assigned to immunized (n = 3) and control (n = 3) groups. The immunized group received three subcutaneous injections of heat-inactivated Staphylococcus epidermidis, while the control group received PBS mixed with adjuvant. At the stage of active immune response, peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll density-gradient centrifugation, and CD45+ immune cells were enriched by fluorescence-activated cell sorting (FACS). Single-cell RNA sequencing (scRNA-seq) libraries were generated using the 10x Genomics Chromium platform.