Comprehensive flow cytometry-based diagnosis of XIAP deficiency.
Dan Tomomasa1, Madoka Nishimura1,2, Ayami Ohya1,3
1Department of Pediatrics and Developmental Biology, Institute of Science Tokyo, Tokyo, Japan.
Clinical and Experimental Immunology
|March 24, 2025
Summary
X-linked inhibitor of apoptosis protein (XIAP) deficiency diagnosis is improved by combining XIAP flow cytometry with muramyl dipeptide (MDP) stimulated TNFα production analysis. This dual approach enhances diagnostic accuracy for inborn errors of immunity.
Area of Science:
- Immunology
- Genetics
- Inborn Errors of Immunity
Background:
- X-linked inhibitor of apoptosis protein (XIAP) deficiency is an X-linked recessive disorder causing immune dysregulation, leading to inflammatory bowel disease and hemophagocytic lymphohistiocytosis.
- Standard XIAP protein expression analysis (XIAP flow) can be unreliable for diagnosing certain XIAP deficiency variants that don't alter protein levels.
- XIAP plays a critical role in the nucleotide-binding and oligomerization domain 2 (NOD2) signaling pathway.
Purpose of the Study:
- To comprehensively analyze nine patients with genetically confirmed XIAP deficiency.
- To evaluate the diagnostic utility of combining XIAP flow cytometry with a novel muramyl dipeptide (MDP) stimulated tumor necrosis factor-alpha (TNFα) production assay (MDP flow).
- To assess the diagnostic accuracy of both XIAP flow and MDP flow methods.
Main Methods:
- Genetic testing was used to confirm XIAP deficiency in nine patients.
- XIAP protein expression was analyzed by flow cytometry (XIAP flow).
- Monocyte TNFα production following muramyl dipeptide (MDP) stimulation was quantified by flow cytometry (MDP flow).
Main Results:
- XIAP flow showed significantly lower median mean fluorescence intensity in patients (195) compared to controls (711) (P < 0.0001).
- MDP flow revealed a significantly lower median percentage of TNFα-producing monocytes in patients (0.34%) versus controls (29.1%) (P = 0.0008).
- Both XIAP flow and MDP flow demonstrated 100% sensitivity and specificity in receiver operating characteristic curve analysis.
Conclusions:
- Combining XIAP flow cytometry with MDP-stimulated TNFα production analysis (MDP flow) provides a highly accurate diagnostic method for XIAP deficiency.
- This combined approach overcomes limitations of XIAP protein expression analysis alone, improving diagnosis of XIAP deficiency.
- The study validates MDP flow as a valuable functional assay for diagnosing XIAP deficiency and related immune disorders.
