Type 1 diabetes (T1D) is an organ specific autoimmune disease resulting in an immune-mediated destruction of insulin-secreting beta cells. The etiology of T1Dis puzzled by a multifaceted interaction of environmental, genetic and epigenetic factors leading to variousendotypesof the disease. Fine mapping of T1D-associated genetic variants with cell-specific epigenetic markers or expression quantitative traits (eQTLs) indicates that the disease riskfactors most probably exert their function by changing the transcriptome profile of immune cells in a cell specific manner. This explains the heterogeneous nature of T1D in terms of both clinical representation and underlying pathogenic pathways. Therefore, measuring the cell-specific transcriptome profile and composition of peripheral immune cells is considered as the key to identify the exact cellular and molecular pathogenic mechanisms of the diseaseprogressand develop novelimmunesignatures for monitoring disease progression.In spite ofextensive research into T1D-associated immune signature, there is still no consensus about T1D-associated immune cell typesand their pathogenic signature.By taking advantage of the unbiased single cell RNA sequencing technology, we profiled transcriptome landscape of peripheral blood mononuclear cells (PBMCs) derived from 40 European T1D subjects and 35 healthy controls matched for age, gender and HLA alleles. We detectedsignificant alteration in relative frequency of several immune cell types(particularly subtypes of CD4+ T, CD8+T, and regulatory Tcells) inT1D subjects compared with healthy controls. Interestingly, we found that the aberrant transcriptome profile of these cell types issignificantly enriched in immune pathwaysassociated with enhanced antigen priming capacity(DAP12 signaling pathway)and transendothelial migratory potential(Rho GTPase activate ROCK pathway) of T cells. Since it is well known that peri-pancreatic lymph nodesare essential for the priming of auto-reactive T cellsin T1D, we hypothesized that the observed signatures in circulating blood cells root from the peri-pancreatic lymph nodes wherein enhanced antigen priming and trans-endothelial migration potential of activated cells lead to the pathogenesis of the disease. To test our hypothesis, the currentproposal aims tocharacterizeimmune subtype proportionand transcriptomic profilein the peri-pancreatic lymph nodes ofT1D cases and controls(aim 1), identify aberrantcell-specific genes/pathways (aim2) and cross-validate lymph node signature using single cell analysis of PBMCs from the same individuals as well as our single cellPBMC datasetfrom the European cohort(aim3). We envisage thatthe current research projectwill work as an essential step for the development of a blood-basedblueprint associated with pathogenesis and progression of the disease.