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Dissection of SAP-dependent and SAP-independent SLAM family signaling in NKT cell development and humoral immunity
Shasha Chen1, Chenxu Cai1, Zehua Li1
1Institute for Immunology and School of Medicine, Tsinghua University, Beijing 100086, China.
Abstract:
Signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) mutations in X-linked lymphoproliferative disease (XLP) lead to defective NKT cell development and impaired humoral immunity. Because of the redundancy of SLAM family receptors (SFRs) and the complexity of SAP actions, how SFRs and SAP mediate these processes remains elusive. Here, we examined NKT cell development and humoral immunity in mice completely deficient in SFR. We found that SFR deficiency severely impaired NKT cell development. In contrast to SAP deficiency, SFR deficiency caused no apparent defect in follicular helper T (TFH) cell differentiation. Intriguingly, the deletion of SFRs completely rescued the severe defect in TFH cell generation caused by SAP deficiency, whereas SFR deletion had a minimal effect on the defective NKT cell development in SAP-deficient mice. These findings suggest that SAP-dependent activating SFR signaling is essential for NKT cell selection; however, SFR signaling is inhibitory in SAP-deficient TFH cells. Thus, our current study revises our understanding of the mechanisms underlying T cell defects in patients with XLP.
Insights
Signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) mutations impair immune cell development. This study reveals SLAM family receptors (SFRs) are crucial for NKT cell development but inhibitory for T follicular helper (TFH) cells when SAP is absent.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Mutations in Signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) cause X-linked lymphoproliferative disease (XLP), leading to immune deficiencies.
- The roles of SLAM family receptors (SFRs) and SAP in immune cell development are complex and not fully understood due to receptor redundancy and SAP's multifaceted actions.
Purpose of the Study:
- To investigate the specific roles of SFRs in NKT cell development and humoral immunity.
- To elucidate the interplay between SAP and SFRs in regulating T follicular helper (TFH) cell differentiation and NKT cell development.
Main Methods:
- Generation and analysis of mice completely deficient in SFRs.
- Comparative analysis of NKT cell development and TFH cell differentiation in wild-type, SAP-deficient, SFR-deficient, and combined SAP/SFR-deficient mice.
Main Results:
- Complete SFR deficiency severely impaired NKT cell development.
- Unlike SAP deficiency, SFR deficiency did not cause defects in TFH cell differentiation.
- Deletion of SFRs rescued TFH cell generation defects in SAP-deficient mice.
- SFR deletion had a minimal impact on NKT cell development in SAP-deficient mice.
Conclusions:
- SAP-dependent activating SFR signaling is essential for NKT cell selection.
- SFR signaling acts inhibitively in SAP-deficient TFH cells, suggesting a context-dependent role.
- This study refines the understanding of T cell defects in X-linked lymphoproliferative disease (XLP).
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