Department of Microbiology, Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Place, New York, NY, 10029, USA.
Baker Institute for Animal Health, College of Veterinary Medicine, Cornell University, Ithaca, NY, 14853, USA.
BMC Biol. 2021 Jan 22;19(1):13. doi: 10.1186/s12915-020-00947-5.
Traditional laboratory model organisms represent a small fraction of the diversity of multicellular life, and findings in any given experimental model often do not translate to other species. Immunology research in non-traditional model organisms can be advantageous or even necessary, such as when studying host-pathogen interactions. However, such research presents multiple challenges, many stemming from an incomplete understanding of potentially species-specific immune cell types, frequencies, and phenotypes. Identifying and characterizing immune cells in such organisms is frequently limited by the availability of species-reactive immunophenotyping reagents for flow cytometry, and insufficient prior knowledge of cell type-defining markers.
Here, we demonstrate the utility of single-cell RNA sequencing (scRNA-Seq) to characterize immune cells for which traditional experimental tools are limited. Specifically, we used scRNA-Seq to comprehensively define the cellular diversity of equine peripheral blood mononuclear cells (PBMC) from healthy horses across different breeds, ages, and sexes. We identified 30 cell type clusters partitioned into five major populations: monocytes/dendritic cells, B cells, CD3PRF1 lymphocytes, CD3PRF1 lymphocytes, and basophils. Comparative analyses revealed many cell populations analogous to human PBMC, including transcriptionally heterogeneous monocytes and distinct dendritic cell subsets (cDC1, cDC2, plasmacytoid DC). Remarkably, we found that a majority of the equine peripheral B cell compartment is comprised of T-bet B cells, an immune cell subpopulation typically associated with chronic infection and inflammation in human and mouse.
Taken together, our results demonstrate the potential of scRNA-Seq for cellular analyses in non-traditional model organisms and form the basis for an immune cell atlas of horse peripheral blood.
传统的实验室模式生物仅代表了多细胞生物多样性的一小部分，在任何特定实验模型中得出的发现通常不适用于其他物种。在非传统模式生物中进行免疫学研究可能具有优势，甚至是必要的，例如在研究宿主-病原体相互作用时。然而，此类研究存在多个挑战，其中许多源于对潜在物种特异性免疫细胞类型、频率和表型的不完全了解。在这些生物体中鉴定和表征免疫细胞通常受到用于流式细胞术的物种反应性免疫表型试剂的可用性以及对细胞类型定义标记物的先前知识不足的限制。
在这里，我们展示了单细胞 RNA 测序（scRNA-Seq）在鉴定传统实验工具受限的免疫细胞方面的实用性。具体来说，我们使用 scRNA-Seq 全面定义了来自不同品种、年龄和性别的健康马外周血单个核细胞（PBMC）的免疫细胞的细胞多样性。我们鉴定出 30 个细胞类型簇，分为五个主要群体：单核细胞/树突状细胞、B 细胞、CD3PRF1 淋巴细胞、CD3PRF1 淋巴细胞和嗜碱性粒细胞。比较分析显示了许多类似于人 PBMC 的细胞群体，包括转录异质性单核细胞和不同的树突状细胞亚群（cDC1、cDC2、浆细胞样树突状细胞）。值得注意的是，我们发现马外周 B 细胞群的大部分由 T-bet B 细胞组成，这是一种免疫细胞亚群，通常与人类和小鼠中的慢性感染和炎症有关。
总之，我们的结果表明 scRNA-Seq 用于非传统模式生物细胞分析的潜力，并为马外周血免疫细胞图谱奠定了基础。
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