Abstract 4142260: Single-cell analysis on peripheral blood mononuclear cells reveals immunodeficiency in pediatric patients with conotruncal defects

Background: Congenital heart diseases (CHD) are the most common birth defects. Previous studies have revealed the susceptibility of CHD patients to immunodeficiency; however, the heterogeneity of immune cells landscape underlying CHD patients remains poorly understood. Research question: Are peripheral blood mononuclear cells dysregulated in pediatric CHD patients? Aims: We aimed to investigate the landscape of peripheral blood mononuclear cells in CHD patients with conotruncal defects by comparison against healthy controls. Methods: Peripheral blood samples were collected in 5 patients with conotruncal defects and 3 healthy children. We conducted single-cell transcriptome analysis on peripheral blood mononuclear cells from these samples. Results: The scheme of whole study was shown in Figure 1A. A total of 44,530 cells were identified after quality-control, clustered into 8 groups, and annotated with canonical PBMC markers (Figure 1B). Compared with healthy controls, patients were characterized with a prominent decrease in natural killer T (NKT) cells and an increased proportion of monocytes were observed (Figure 1C). Zooming into NK-like cells confirmed a significant contribution of NKT cells in difference between groups, whilst other types were similar in both groups (Figure 2A). The differentially expressed gene in NKT were enriched in pathway involving T helper cells differentiation, signal transduction and regulation (Figure 2B). Furthermore, NKT in patients showed a significantly lower proliferation score in contrast with a higher apoptosis score (Figure 2C&D). Although monocytes in patients were more in quantity, the composition of CD14 + and CD16 + subtypes were comparable between groups (Figure 3A). Concordantly, apoptosis score of monocytes were similar. However, the T cell proliferation score was lower in case group (Figure 3B&C). In addition, CD14 + and CD16 + monocytes both showed distinct transcriptome between groups and the differentially expressed genes were prevalently enriched in inflammation-related pathways (Figure 3D&E). Conclusion: Single-cell analysis revealed a dysregulated PBMC landscape in pediatric patients with conotruncal defects, exhibiting a prominent decrease in NKT population and an increased proportion of monocytes. Transcriptome analysis further indicated a less mature immune phenotype in NKT and monocytes differentiation. Future study is warranted to further investigate the roles of these cells on immunoregulation in these patients.