RESUMO
Antigen presenting cells (APCs) in the thymus play an essential role in the establishment of central tolerance, i.e. the generation of a repertoire of functional and self-tolerant T cells to prevent autoimmunity. In this study, we have compared the transcriptomes of four primary APCs from human thymus (mTECs, CD19+ B cells, CD141+ and CD123+ DCs). We investigated a set of genes including the HLA genes, genes encoding transcriptional regulators and finally, tissue-enriched genes, i.e, genes with a five-fold higher expression in a particular human tissue. We show that thymic CD141+ DCs express the highest levels of all classical HLA genes and 67% (14/21) of the HLA class I and II pathway genes investigated in this study. CD141+ DCs also expressed the highest levels of the transcriptional regulator DEAF1, whereas AIRE and FEZF2 expression were mainly found in primary human mTECs. We found expression of "tissue enriched genes" from the Human Protein Atlas (HPA) in all four APC types, but the mTECs were clearly dominating in the number of uniquely expressed tissue enriched genes (20% in mTECs, 7% in CD19+ B cells, 4% in CD123+ DCs and 2% in CD141+ DCs). The tissue enriched genes also overlapped with reported human autoantigens. This is, to our knowledge, the first study that performs RNA sequencing of mTECs, CD19+ B cells, CD141+ and CD123+ DCs isolated from the same individuals and provides insight into the transcriptomes of these human thymic APCs.
Assuntos
Linfócitos B/imunologia , Células Dendríticas/imunologia , Células Epiteliais/imunologia , Antígenos HLA/imunologia , Timo/imunologia , Transcriptoma/imunologia , Apresentação de Antígeno/genética , Antígenos de Superfície/genética , Antígenos de Superfície/imunologia , Linfócitos B/citologia , Linfócitos B/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/imunologia , Células Dendríticas/citologia , Células Dendríticas/metabolismo , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Perfilação da Expressão Gênica , Antígenos HLA/classificação , Antígenos HLA/genética , Humanos , Imunofenotipagem , Lactente , Recém-Nascido , Subunidade alfa de Receptor de Interleucina-3/genética , Subunidade alfa de Receptor de Interleucina-3/imunologia , Masculino , Cultura Primária de Células , Trombomodulina , Timo/citologia , Timo/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/imunologia , Proteína AIRERESUMO
Genome-wide association studies (GWAS) have boosted our knowledge of genetic risk variants in autoimmune diseases (AIDs). Most risk variants are located within or near genes with immunological functions, and the majority is found to be non-coding, pointing towards a regulatory role. In this study, we performed a cis expression quantitative trait locus (eQTL) screen restricted to 353 AID associated risk variants selected from the GWAS catalog to investigate whether these single nucleotide polymorphisms (SNPs) influence gene expression in thymus. Genotypes were obtained by Immunochip (Ichip) and tested against expression of surrounding genes (±1 Mb) in human thymic tissue (n = 42). We identified eight significant eQTLs located within seven genetic regions (FCRL3, RNASET2, C2orf74, NPIPB8, SIRPG, SYS1 and AJ006998.2) where the expression was associated with AID risk SNPs at a study-wide level of significance (P < 2.7 × 10-5). In NPIPB8 and AJ006998.2, the eQTL signals appeared to be thymus-specific. Furthermore, many AID risk SNPs from GWAS have been subsequently fine-mapped in recent Ichip projects, and fine-mapped AID SNPs overlapped with the thymic eQTLs within RNASET2 and SIRPG Finally, in all the eQTL regions, except C2orf74, SNPs underlying the thymic eQTLs were predicted to interfere with transcription factors important in T cell development. Our study therefore reveals autoimmune risk variants that act as eQTLs in thymus, and suggest that thymic gene regulation may play a functional role at some AID risk loci.