Background/Purpose: The family of signaling lymphocyte activating molecules (SLAM) have been shown to play a key role in the development of autoimmunity in spontaneous and induced mouse models. Previous work by others has shown that expression of two SLAM family members, CD150 and Ly108, plays a critical role in the development of Natural Killer T (NKT) cells, an innate-like semi-invariant population of lymphocytes, which quickly respond to lipids presented on non-classical MHCs. However, the impact of SLAM polymorphisms on NKT function is less clear. The aim of this study was to characterize both the development and function of NKT cells in B6 congenic mice with an NZB chromosome 1 interval that is known to have polymorphisms in the SLAM family of molecules. 

Methods:  NKT development and marker expression were examined by flow cytometry of de novo splenocytes and thymocytes. NKT cell function was examined by in vivo stimulation with 2µg of αGalCer, injected intravenously. Production of IFNγ and IL-4 was measured by intracellular flow cytometry. Bone marrow derived dendritic cells (BMDCs) were generated by 7-10 day culture with recombinant human FLT3 ligand.

Results:  Congenic mice had significantly fewer splenic NKT cells when compared to B6 controls.  However, NKT cell frequencies in the thymus did not differ. The frequency of double positive thymocytes, critical for homotypic interactions between NKT cell precursors, was also unchanged.  In support of previous findings, cell surface expression of SLAM family members on this cell population was altered. When compared to control animals, NZB congenic mice had significantly decreased expression of positive signaling Ly108 and CD150 molecules and increased expression of the negative SLAM signaling molecule, Ly9. Since NKT cells have been shown to play a role in autoimmunity through production of cytokines such as IL-4 and IFNγ, the capacity of these cells to secrete cytokines was assessed. Upon stimulation with αGalCer, the prototypic NKT cell stimulating lipid, NKT cells from NZB congenic mice produced significantly less IL-4 and IFNγ when compared to control mice.  Consistent with this being the result of the SLAM polymorphisms, analysis of subcongenic NZB strains with shorter chromosome 1 intervals revealed that both of these phenotypes localized to a small region between 171-177Mb containing the SLAM family. To determine whether the reduced NKT cytokine production in NZB congenic mice was due to altered antigen presentation or impaired NKT cell function, adoptive transfer experiments were conducted with αGalCer pulsed BMDCs from control or congenic mice. The results revealed that injection of BMDCs generated from either strain could equivalently stimulate IL- 4 and IFNγ production by NKT cells in control animals, whereas injection of control BMDCs into NZB congenic mice resulted in impaired production of these cytokines.

Conclusion: These data suggest that polymorphisms in the SLAM family result in reduced peripheral NKT cell numbers and an intrinsic NKT cell functional defect.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/polymorphisms-in-the-slam-family-of-molecules-play-a-role-in-the-development-and-function-of-invariant-natural-killer-t-cells-in-new-zealand-black-mice/