CD4⁺ T Cell Subsets and PTPN22 as Novel Biomarkers of Immune Dysregulation in Dilated Cardiomyopathy

Recent multiomics advancements have improved our understanding of immune dysregulation in dilated cardiomyopathy (DCM). However, specific immune cell subsets and their regulatory genes are still ambiguous. This study aimed to explore immune cell imbalances and regulatory genes in DCM, discover diagnostic biomarkers, and identify potential therapeutic targets. Immune cell infiltration in DCM patients was quantified via deconvolution algorithms and single-cell RNA sequencing. Flow cytometry validation in 40 DCM patients and 40 healthy controls confirmed a notable increase in CD4⁺ effector memory T cells (CD4⁺ TEM cells) in DCM patients. Differential expression analysis of the GSE101585 dataset revealed 1783 genes. Weighted gene coexpression network analysis (WGCNA) identified a core immune-regulatory gene set, and protein-protein interaction (PPI) analysis highlighted 36 hub genes. Machine learning cross-validation identified four diagnostic biomarkers (LRRTM4, PTPN22, FAM175B, and PROM2) whose transcriptional changes had been validated by qPCR. Among these genes, PTPN22 was strongly correlated with CD4⁺ TEM cell abundance. Additionally, DSigDB analysis predicted 87 potential therapeutic drugs, with PTPN22 being the target of the most drugs. This study reveals a CD4⁺ T cell subset-centered immunoregulatory network in DCM, identifying novel diagnostic biomarkers and druggable targets to guide precision immunomodulatory strategies for DCM management.