TLR9 engagement on CD4 T lymphocytes represses gamma-radiation-induced apoptosis through activation of checkpoint kinase response elements.

T cell-based therapies have much promise in cancer treatment. This approach may be enhanced if used in combination with radiotherapy provided that tumor-specific T cells can be protected against the effects of radiotherapy. Previously, we demonstrated that administration of TLR9 ligand into mice decreased activation- and serum deprivation-induced cell death in T cells. We hypothesized that TLR9 engagement on T lymphocytes decreased apoptosis after cellular stress. We show that TLR9 engagement on murine CD4 T cells reduces gamma-radiation-induced apoptosis as judged by decreased annexin-V/PI staining, caspase-3 activation, and PARP cleavage. TLR9-stimulated cells show heightened accumulation at the G2 cell-cycle phase and increased DNA repair rates. Irradiated, TLR9-engaged cells showed higher levels of phosphorylated Chk1 and Chk2. While the levels of activated ATM in response to IR did not differ between TLR9-stimulated and unstimulated cells, inhibition of ATM/ATR and Chk1/Chk2 kinases abolished the radioprotective effects in TLR9-stimulated cells. In vivo, TLR9-stimulated cells displayed higher radio resistance than TLR9-stimulated MyD88(-/-) T cells and responded to antigenic stimulation after total body irradiation. These findings show, for the first time, that TLR9 engagement on CD4 T cells reduces IR-induced apoptosis by influencing cell-cycle checkpoint activity, potentially allowing for combinatorial immunotherapy and radiotherapy.

Identification of quantitative trait Loci that affect aggressive behavior in mice.

Despite the previous development of single-gene knock-out mice that exhibit alterations in aggressive behavior, very little progress has been made toward identifying the natural gene variants (alleles) that contribute to individual or strain differences in aggression. Whereas most inbred mouse strains show an intermediate level of inter-male aggression in the resident-intruder or dangler behavioral tests, NZB/B1NJ mice are extremely aggressive and A/J mice are extremely unaggressive. We took advantage of the large phenotypic difference between these strains and used an outcross-backcross breeding protocol and a genome-wide scan to identify aggression quantitative trait loci (QTLs) on distal chromosome 10 (Aggr1; p = 6 x 10(-7)) and proximal chromosome X (Aggr2; p = 2.14 x 10(-5)). Candidate genes for Aggr1 and Aggr2, respectively, include the diacylglycerol kinase alpha subunit gene (Dagk1) and the glutamate receptor subunit AMPA3 gene (Gria3). This is the first report of significant aggression QTLs established through a genome-wide scan in any mammal. The mapping of these QTLs is a step toward the definitive identification of mouse alleles that affect aggression and may lead, ultimately, to the discovery of homologous alleles that affect individual differences in aggression within other mammalian species.