Role of IFN-gamma on innate immune cell-mediated protective mechanisms during Salmonella infection
Final Report Abstract
In my first project I have examined which DC subsets are involved in priming of Herpes simplex virus type 1 (HSV-1)-specific CD8+ T cells after flank infection. Using the Rosa-DTA (R-DTA) mouse model that carries a floxed-STOP cassette in front of a Diphtheria toxin subunit within the ROSA26 locus and infecting these mice with HSV-1 expressing the Cre recominase, the STOP cassette can be selectively excised in HSV-1-infected cells resulting in Diphtheria toxinmediated cell death. This approach allowed me to selectively deplete HSV-1-infected cells and eliminate potential direct antigen-presentation by infected DC. Using this R-DTA system I could show ex vivo and in vivo that CD8+ T cell priming mainly occurred via CD8α+ DC-mediated cross-presentation of viral antigens. These findings are consistent with a model in which skinresident DC that are either directly infected or have taken up virally-infected material migrate to the draining lymph nodes and hand their cargo over to lymph node-resident CD8α+ DC for cross-priming of CD8+ T cells. Resident memory T cells (TRM) are a unique subset of memory cells that lodged into tissues such as the skin during the early phase of a peripheral infection or injury, become sessile there and provide effective protection against reinfection. Studies done with germfree (GF) mice demonstrated that the absence of microbial signals impacted on the ability of effector T cells located in the skin to provide protection during infection. In my second project, I have investigated a potential role for microbiota on the maintenance of TRM cells in the skin utilizing a model of unspecific lodgement of transferred in vitro activated CD8+ T cells (gBT-I) using the contact-sensitizing agent DFNB. Surprisingly, injected T cells developed into CD103+CD69+ TRM and were found at the same frequency in GF and B6 mice in the skin 30 days after DNFB treatment suggesting that TRM precursors do not rely on stimuli from microorganisms to lodge into the skin and differentiate into TRM. Intriguingly, the number of circulatory gBT-I T cells in the spleen differed significantly between GF and B6 mice with the majority of cells having a CD103-CD44+CD62L+ central memory T cell phenotype. To unravel the factors/pathways that might be involved in the survival of gBT-I in SPF mice, transferred gBT-I cells from B6 and GF mice were re-isolated 7 days later and FACSAria II sorted. The mRNA was extracted and subjected to high-throughput deep sequencing using Hiseq2000 which has been done shortly after my funding period has finished. This project is now continued by members of Dr. Sammy Bedoui’s research group and has produced very promising preliminary data on TGF signalling being one of the major drivers in the survival of memory CD8+ T cells in the spleen of SPF mice versus GF mice.
Publications
- (2015). CD69 interference with sphingosine-1-phosphate receptor function regulates peripheral T cell retention. Cutting Edge: J Immunol
Mackay L.K., A. Braun, B.L. Macleod, N. Collins, C. Tebartz, S. Bedoui, F.R. Carbone and T. Gebardt
(See online at https://doi.org/10.4049/jimmunol.1402256) - NLRP3 inflammasome activation downstream of cytoplasmic LPS recognition by both caspase-4 and caspase-5. Eur J Immunol Volume 45, Issue 10, October 2015, Pages 2918-2926
Baker P.J., D. Boucher, D. Bierschenk, C. Tebartz, P.G. Whitney, D.B. D’Silva, M.C. Tanzer, Mercedes Monteleone Avril A. B. Robertson, Matthew A. Cooper, S.Alvarez-Diaz, M. Herold, S. Bedoui, K. Schroder, S.L. Masters
(See online at https://doi.org/10.1002/eji.201545655)
