Decrease of spleen invariant natural killer T and natural killer cell numbers in Burkholderia thailandensis-infected C57BL/6 mice

Thitinan Kasetthat,¹ Rasana W. Sermswan,^2,3 Yue Ren,^4,5 Hiroshi Watarai,⁴ Surasakdi Wongratanacheewin^1,3

¹ Department of Microbiology,
² Department of Biochemistry,
³ Meliodosis Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
⁴ Department of Immunology and Stem Cell Biology, Faculty of Medicine, Institute of Medical Science, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Japan
⁵ Department of Neurology, The Neurological Institute of Jiangxi Province, Jiangxi Provincial People’s Hospital, Nanchang, China

Abstract

Background: Burkholderia thailandensis is a non-pathogenic bacterium that is closely related to B. pseudomallei. Invariant natural killer T (iNKT) cells are innate lymphoid cells that play a role in bacterial infections; however the iNKT cells in B. thailandensis infections are still uncharacterized.
Objectives: To study the cytokine production in α-galactosylceramide (α-GalCer)-stimulated lymphocytes from mouse organs. The numbers of spleen iNKT cells, natural killer (NK) cells, dendritic cells and macrophages in B. thailandensis-infected C57BL/6 (B6) mice were investigated.
Methods: Lymphocytes, obtained from mouse lungs, livers, and spleens, were cultured for 48 hours with α-GalCer, and their cytokine levels were determined. iNKT, dendritic, macrophage and NK cells in the spleen of B. thailandensis-infected B6 mice or iNKT knock out (KO) mice, stimulated with either phosphate-buffered saline (PBS) or α-GalCer, were analyzed by flow cytometry. This was also done in adoptive cell transfer experiments.
Results: Interferon gamma (IFN-γ) was predominantly produced in α-GalCer-stimulated mouse spleen and liver lymphocytes, while interleukin (IL)-13 was the main cytokine found in the lungs. B. thailandensis-infected mice had a significantly lower number of splenic iNKT, NK and dendritic cells, but not macrophages, compared to the control. Interestingly, the number of NK cells was significantly decreased in iNKT wild type and iNKT KO mice after B. thailandensis infection. The number of NK cells recovered by activation with α-GalCer or after adoptive transfer of iNKT cells into KO mice. The iNKT cell-mediated reduction of dendritic and NK cells might be related to infection by B. thailandensis.
Conclusion: B. thailandensis decreased the number of iNKT and NK cells in the spleen of infected mice.
Key words: iNKT cells, B. thailandensis, α-GalCer, iNKT knockout B6 mice, Melioidosis,