Characterizing expression profiles of turkey immune cell populations within peripheral blood using single-cell transcriptomics

Authors: Monson, Melissa; SHARMA, SHARU PAUL - Iowa State University; Byrne, Kristen; Loving, Crystal

Submitted to: Avian Immunology Group Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Understanding how the turkey immune system interacts with pathogens requires the ability to distinguish immune cell-type specific responses. However, antibody-based methods for detection and differentiation of leukocytes are limited for turkeys. Single-cell RNA-sequencing (scRNA-seq) can resolve individual immune cells into distinct populations based on their transcriptional profiles, without the need for cell-type specific reagents. To gain insight into expression patterns within turkey immune cells, blood samples collected from two turkeys were divided and used to isolate peripheral blood mononuclear cells (PBMCs) or all white blood cells (WBCs). Approximately 80,000 cells were sequenced, with around 22,000 cells per PBMC library and 18,000 cells per WBC library. WBC and PBMC datasets were analyzed separately due to known differences in cell type composition, specifically the presence or absence of the heterophil populations within the isolated samples. Datasets were filtered, normalized, and clustered using the Seurat package. Initial clustering at a resolution of 0.1 identified 11 cell clusters within turkey PBMCs and 13 clusters in WBCs. Based on expression of marker genes, cells predicted to be thrombocytes were most abundant, followed by heterophils (in WBCs only) and then T lymphocytes (specifically helper T cells). Sub-clustering of the initial clusters of lymphocytes and monocytes was performed to predict cell subtypes and their characteristic gene expression patterns. For example, multiple granzyme and NK-lysin effector genes had variable expression between cytotoxic T cell clusters. Transcriptional profiles for cell types observed in both PBMCs and WBCs were also compared to investigate differences due to isolation method. Overall, both canonical and novel cell-type specific markers were identified, revealing pathways for future functional investigations within these cell types and genes that can be used to identify turkey leukocyte populations in future research. Using single-cell transcriptomics to investigate turkey immune subtypes has potential to disentangle their roles in immune recognition and clearance or tolerance of the wide diversity of pathogens in the turkey.