| domain | established finding | quantitative/patient evidence | evidence type | ontology suggestions |
|---|---|---|---|---|
| Gene / inheritance | CD3G deficiency is an ultrarare autosomal-recessive inborn error of immunity caused by biallelic CD3G variants; disease spectrum spans combined immunodeficiency with immune dysregulation rather than uniformly classic SCID. | 2019 review found 10 reported cases from 5 unrelated families; 2021 report noted 14 previously reported cases; later 2026 synthesis reported 18 total patients and explicitly called the disorder autosomal recessive (later than requested 2023-2024 window) (pqac-00000000, pqac-00000005, pqac-00000006) | Human case series/review | MONDO:0014276; CD3G (HGNC gene); HP:0000007 Autosomal recessive inheritance; NCIT: Inborn Error of Immunity |
| TCR-CD3 mechanism | CD3γ is required for optimal surface expression of the TCR/CD3 complex; deficiency lowers CD3ε and TCRαβ expression and weakens TCR signaling without abolishing polyclonal T-cell development in humans. | In 6 bi-allelic cases, all showed markedly reduced CD3ε/TCRαβ on T cells and impaired proliferation to PHA; anti-CD3/CD28 partly restored responses (pqac-00000011). Later 2026 cases also had reduced TCR/CD3 expression despite normal T-cell counts (pqac-00000016) | Human functional immunology | GO:0050852 T cell receptor signaling pathway; GO:0042102 positive regulation of T cell proliferation; CL:0000624 CD4-positive, alpha-beta T cell; CL:0000625 CD8-positive, alpha-beta T cell |
| Infections | Clinical infectious susceptibility is variable, from recurrent sinopulmonary infections to severe/opportunistic infections. | 2019 analysis: infections in 7 patients; 4/5 with sinopulmonary infections developed bronchiectasis; reported opportunistic infections included Candida, Giardia, and severe EBV; one patient had pneumonia by 6-9 months and EBV viremia 102,000 copies/mL (pqac-00000002, pqac-00000005) | Human case reports/review | HP:0002719 Recurrent infections; HP:0012735 Recurrent respiratory infections; HP:0002110 Bronchiectasis; NCBITaxon:10376 Epstein-Barr virus |
| Autoimmunity / immune dysregulation | Autoimmunity is a major and often dominant manifestation; autoimmune cytopenias, thyroiditis, enteropathy/IBD-like disease, vitiligo, hepatitis, and Evans syndrome are reported. | In one 2014 family series, 5/5 had autoimmune thyroiditis, 2/5 autoimmune hemolytic anemia, 1/5 immune thrombocytopenia, 1/5 autoimmune hepatitis, 1/5 vitiligo (pqac-00000004). In the 2018 cohort, all 6 patients had autoimmunity (pqac-00000011). Later 2026 adult cases highlighted Evans syndrome responsive to rituximab (later than requested window) (pqac-00000017) | Human case series | HP:0002716 Autoimmunity; HP:0001890 Autoimmune hemolytic anemia; HP:0001973 Autoimmune thrombocytopenia; HP:0000824 Autoimmune thyroiditis; HP:0002037 Inflammatory bowel disease; HP:0005603 Vitiligo |
| Laboratory phenotype | Typical immunophenotype includes reduced TCR/CD3 surface expression, reduced naïve T cells, variable CD4/CD8 lymphopenia, hypogammaglobulinemia, impaired vaccine responses, reduced switched memory B cells, and sometimes high IgE. | 2014 series: all 5 had low CD3+TCRαβ+ percentages; only 1 had overall lymphopenia; 3 had CD3+ T-cell lymphopenia; 3/5 had high IgE; 3/5 had ANA positivity (pqac-00000004). 2021 case: CD4 count 627/µL, IgG 338 mg/dL, impaired vaccination responses (pqac-00000019). 2019 case had decreased switched memory B cells and diminished CD40L expression (pqac-00000000) | Human laboratory/clinical | HP:0005403 Decreased alpha-beta T-cell count; HP:0002841 Hypogammaglobulinemia; HP:0010976 Reduced memory B-cell count; HP:0002910 Elevated IgE level; HP:0002720 Impaired vaccine response |
| Treg / tolerance mechanism | A leading mechanism of immune dysregulation is defective regulatory T-cell biology: reduced Treg proportion/diversity, restricted TCR repertoire, impaired suppressive function, and enrichment of self-reactive conventional T cells. | In the 2018 study, Treg cells from CD3G-mutated patients failed to suppress Teff proliferation at 1:2 ratios and showed reduced suppression at 1:1 ratios; 6 patients showed repertoire restriction and self-reactivity signatures (pqac-00000008, pqac-00000009) | Human mechanistic study | GO:0002507 tolerance induction; GO:0043029 T cell homeostasis; CL:0000815 regulatory T cell; HP:0002960 Autoimmune disease |
| B-cell / humoral involvement | Some patients show a CVID-like or predominant humoral phenotype, indicating downstream B-cell dysfunction despite the primary T-cell signaling defect. | 2019 Taiwanese adult case had recurrent sinopulmonary infections, hypogammaglobulinemia, decreased switched memory B cells, diminished CD40L expression, and 20 years of immunoglobulin replacement, yet no overt autoimmunity (pqac-00000000, pqac-00000003, pqac-00000012) | Human case report | HP:0002721 Immunoglobulin deficiency; HP:0010976 Reduced memory B-cell count; NCIT: Common Variable Immunodeficiency-like phenotype |
| Diagnosis | Diagnosis relies on clinical suspicion for CID/immune dysregulation plus flow cytometry showing reduced TCR/CD3 expression and confirmatory sequencing (targeted NGS, WES, or WGS). | 2024 Algerian flow-cytometry experience reported CD3γ deficiency diagnosed in 2 siblings presenting with recurrent infections; the paper emphasized FCM as a direct or highly informative IEI diagnostic tool (paper search summary). 2024 WES study from Türkiye supports molecular diagnosis in IEI cohorts though not CD3G-specific in the excerpt (paper search summary; pqac-00000016) | Human diagnostic practice / cohort | NCIT: Flow Cytometry; NCIT: Whole Exome Sequencing; NCIT: Whole Genome Sequencing; NCIT: Genetic Testing |
| Treatment | Management is individualized and case-based: immunoglobulin replacement, prophylactic/therapeutic antimicrobials, steroids, rituximab, sirolimus, and HSCT in severe cases. | 2019 patient received IVIG for ~20 years plus antibiotics/steroids (pqac-00000003). 2021 patient received immunoglobulin replacement, antibiotics, rituximab, sirolimus, steroids (pqac-00000019). Severe life-threatening infections requiring HSCT were associated with worse outcomes in 2019 analysis (pqac-00000000) | Human case reports/review | NCIT:C80687 Immunoglobulin Therapy; NCIT:C15543 Anti-Infective Therapy; NCIT:C1802 Rituximab; NCIT:C29457 Sirolimus; NCIT:C15206 Hematopoietic Stem Cell Transplantation |
| Prognosis | Prognosis is highly variable, from isolated autoimmune thyroiditis to fatal infantile disease; severe infections, opportunistic infections, IBD-like disease, and HSCT-related complications drive poorer outcomes. | 2019 review reported 3 deaths: severe infection at 31 months, post-transplant viral pneumonia at 17 months, and graft-versus-host disease at 47 months; worse prognosis associated with opportunistic infections (p=0.0124), severe life-threatening infections needing HSCT (p=0.01), and IBD-like diarrhea (p=0.0124); autoimmune thyroiditis associated with better prognosis (p=0.0124) (pqac-00000000, pqac-00000002) | Human case aggregation | HP:0003819 Death in infancy; HP:0006538 Chronic course; HP:0002583 Chronic diarrhea; NCIT: Prognosis |
| Epidemiology limits | No robust population prevalence, incidence, carrier-frequency, penetrance, or sex-ratio estimates were identified; evidence remains almost entirely from published families/case reports. | Disease totals in the literature remained in the low double digits across reports (10, 14, then 18 in later 2026 synthesis) (pqac-00000000, pqac-00000005, pqac-00000006) | Evidence-gap statement from literature scope | NCIT: Rare Disease; MONDO:0014276 |
| Environmental / infectious modifiers | No disease-specific environmental or lifestyle risk factors were identified; infectious exposures act mainly as complications or triggers that reveal the immune defect. | Reported pathogens/complications include H. influenzae, Pseudomonas aeruginosa, S. aureus cellulitis, E. coli epididymoorchitis, EBV viremia, Candida, Giardia, and H. pylori-associated gastric MALT lymphoma in a later 2026 report (later than requested window) (pqac-00000003, pqac-00000016) | Human case reports | NCBITaxon:727 Haemophilus influenzae; NCBITaxon:287 Pseudomonas aeruginosa; NCBITaxon:1280 Staphylococcus aureus; NCBITaxon:562 Escherichia coli; NCBITaxon:210 Helicobacter pylori |
| Model-organism limitations | Mouse CD3-chain knockout biology does not fully recapitulate human disease; no single CD3 subunit is absolutely required for murine T-cell maturation, limiting direct translation from knockout models. Human-CD3 replacement mice are useful for therapeutic studies but are not disease models of CD3G deficiency. | Review evidence notes fundamental mouse-human differences in CD3 subunit requirements (pqac-00000013). Human CD3E/D/G-replaced mice are immune competent and were developed to test human CD3-directed therapeutics, not to model CD3G deficiency pathogenesis (paper search summary for Ueda 2017) | Comparative/model evidence | NCBITaxon:10090 Mus musculus; GO:0046649 lymphocyte activation; NCIT: Disease Model |


*Table: This table condenses the strongest gathered evidence on combined immunodeficiency due to CD3G deficiency across genetics, mechanism, phenotype, diagnosis, treatment, prognosis, and model limitations. It is designed for rapid knowledge-base ingestion and flags where later 2026 evidence falls outside the user's preferred 2023-2024 priority window.*