Genes with mutations that cause monogenic, severe T-cell immunodeficiency in humans can be intrinsic to the thymic epithelium or to T cells. (A) Genetic defects that are intrinsic to thymic epithelial cells ultimately affect the antigen-presentation pathway. (B) Genetic defects that are intrinsic to T cells include those that affect T-cell receptor (TCR) signaling, cytokine signaling, somatic recombination, or basic cellular processes. Other genes that are important to these pathways or processes, but have not been linked to severe T-cell deficiency in humans are shown in grey. Copyright © 2008. Nature Publishing Group. Adapted with permission from Liston A, Enders A, Siggs OM. Unravelling the association of partial T-cell immunodeficiency and immune dysregulation. Nat Rev Immunol. 2008;8:546.80Abbreviations: ADA, adenosine deaminase; ATM, ataxia-telangiectasia mutated; CBL, Casitas B-lineage lymphoma; CIITA, class II transactivator; DCLRE1C, DNA crosslink repair 1C; DNMT3β, DNA cytosine-5 methyltransferase 3β; ER, endoplasmic reticulum; FOXN1, forkhead box N1; GADS, GRB2-related adaptor protein; IL-2RΓ, IL-2 receptor Γ-chain; IL-7, interleukin-7; IL-7Rα, IL-7 receptor α-chain; JAK, Janus kinase; LAT, linker for activation of T cells; LIG4, ligase IV; MRE11A, meiotic recombination 11 homolog A; Nibrin, Nijmegen breakage syndrome 1; NP, nucleoside phosphorylase; CRACM1, calcium release-activated calcium modulator 1; RAG, recombination-activating gene; RFX5, regulatory factor X5; RFXANK, RFX-associated ankyrin-containing protein; RFXAP, RFX-associated protein; RMRP, RNA component of mitochondrial RNA-processing endoribonuclease; SLP76, SRC-homology-2-domain-containing leukocyte protein of 76 kDa; SMARCAL1, SWI/SNF-related matrix-associated actin-dependent regulator of chromatin a-like 1; SP110, SP110 nuclear body protein; STAT5B, signal transducer and activator of transcription 5B; TAP, transporter associated with antigen processing; TAPBP, TAP-binding protein; TSAD, T-cell-specific adaptor protein; ZAP70, ζ-chain-associated protein kinase of 70 kDa. The genetic basis of severe combined immunodeficiency and its variants. Tasher D, Dalal I - The application of clinical genetics (2012). Not Altered. CC.