Tolerance of the semi-allogeneic fetus presents a significant challenge to the maternal immune system. The effect of pregnancy on maternal cellular immunity was established by assessing maternal effector and regulatory T-cell subsets during human pregnancy. This demonstrated that an increase in maternal peripheral regulatory T-cells or a shift from a Th1 to Th2 phenotype was not a requirement for normal pregnancy. We also determined the profound impact of maternal Cytomegalovirus seropositivity on maternal T- cell dynamics. T-cells with specificity for fetal epitopes have been detected in women with a history of pregnancy but it has been thought that such fetal specific cells were deleted during pregnancy. We identified, using MHC-peptide multimers, fetal-specific CD8 T-cells in half of all pregnancies. The fetal-specific response increased during pregnancy and persisted in the post natal period. Fetal-specific cells demonstrated an effector memory phenotype and retained functional potential. These data show that the development of a fetal-specific adaptive cellular immune response is a normal consequence of human pregnancy. Women with recurrent miscarriage were found to have abnormal T-cell function, with increased IFN\(\gamma\) and Il-17 production. Fetal specific T-cells were also detected in this cohort and progesterone attenuated their function, which may have therapeutic implications.

The ability to generate a tumour-reactive T cell compartment is possible through the genetic engineering of patient T cells with tumour-reactive TCRs or CARs. The clinical testing of such therapies is garnering increasingly encouraging results, particularly in haematological malignancies. However, identification of more potent and specific target antigens, and combating immunosuppression in the tumour microenvironment is necessary to transfer these clinical responses to solid tumours. We investigated whether recurrent cancer mutations encode immunogenic neoantigens presented by common HLA class I alleles. We isolated TCRs specific for putative neoepitopes derived from common mutations in calreticulin (mCALR), and FBXW7. These TCRs showed moderate affinity but fine peptide specificity for mutant peptides, with some TCRs capable of recognising mutant cell lines. However, mass spectral analysis of MHC-eluted peptides and MHC class I tetramer staining of patient T cells suggested putative mCALR neoepitopes were not naturally processed and presented. Finally, we investigated whether ectopic expression of arginine recycling enzymes argininosuccinate synthetase (ASS) and/or ornithine transcarbamylase (OTC) in CAR T cells endows resistance to immunosuppression driven by arginine depletion. Increased ASS/OTC expression and function was detected in CAR-engineered T cells, however enhanced cytotoxicity and proliferation of CAR T cells was not observed following arginine depletion.

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