Jessica Carter

Pro-inflammatory T-lymphocytes rapidly infiltrate into the brain and contribute to neuronal injury following cardiac arrest and cardiopulmonary resuscitation.

Although inflammatory mechanisms have been linked to neuronal injury following global cerebral ischemia, the presence of infiltrating peripheral immune cells remains understudied. We performed flow cytometry of single cell suspensions obtained from the brains of mice at varying time points after global cerebral ischemia induced by cardiac arrest and cardiopulmonary resuscitation (CA/CPR) to characterize the influx of lymphocytes into the injured brain. We observed that CA/CPR caused a large influx of lymphocytes within 3h of resuscitation that was maintained for the 3day duration of our experiments. Using cell staining flow cytometry we observed that the large majority of infiltrating lymphocytes were CD4(+) T cells. Intracellular stains revealed a large proportion of pro-inflammatory T cells expressing either TNFα or INFγ. Importantly, the lack of functional T cells in TCRα knockout mice reduced neuronal injury following CA/CPR, implicating pro-inflammatory T cells in the progression of ischemic neuronal injury. Finally, we made the remarkable observation that the novel CD4(+)CD40(+) (Th40) population of pro-inflammatory T cells that are strongly associated with autoimmunity are present in large numbers in the injured brain. These data indicate that studies investigating the neuro-immune response after global cerebral ischemia should consider the role of infiltrating T cells in orchestrating the acute and sustained immune response.

CD40 engagement of CD4+CD40+ T cells in a neo‐self antigen disease model ablates CTLA‐4 expression and indirectly impacts tolerance

Biomarkers defining pathogenic effector T (Teff) cells slowly have been forthcoming and towards this we identified CD4+ T cells that express CD40 (CD4+CD40+) as pathogenic in the NOD type 1 diabetes (T1D) model. CD4+CD40+ T cells rapidly and efficiently transfer T1D to NOD.scid recipients. To study the origin of CD4+CD40+ T cells and disease pathogenesis, we employed a dual transgenic model expressing OVA323–339 peptide as a neo‐self antigen on islet β cells and medullary thymic epithelial cells (mTECs) and a transgenic TCR recognizing the OVA323–339 peptide. CD4+CD40+ T cells and Treg cells each recognizing the cognate neo‐antigen, rather than being deleted through central tolerance, drastically expanded in the thymus. In pancreatic lymph nodes of DO11.RIPmOVA mice, CD4+CD40+ T cells and Treg cells are expanded in number compared with DO11 mice and importantly, Treg cells remain functional throughout the disease process. When exposed to neo‐self antigen, CD4+CD40+ T cells do not express the auto‐regulatory CTLA‐4 molecule while naïve CD4+CD40+ T cells do. DO11.RIPmOVA mice develop autoimmune‐type diabetes. CD40 engagement has been shown to prevent CTLA‐4 expression and injecting anti‐CD40 in DO11.RIPmOVA mice significantly exacerbates disease. These data suggest a unique means by which CD4+CD40+ T cells thwart tolerance.

Defining a new biomarker for the autoimmune component of Multiple Sclerosis: Th40 cells

Multiple Sclerosis (MS) is a chronic inflammatory, neurodegenerative disease. Diagnosis is very difficult requiring defined symptoms and multiple CNS imaging. A complicating issue is that almost all symptoms are not disease specific for MS. Autoimmunity is evident, yet the only immune-related diagnostic tool is cerebral-spinal fluid examination for oligoclonal bands. This study addresses the impact of Th40 cells, a pathogenic effector subset of helper T cells, in MS. MS patients including relapsing/remitting MS, secondary progressive MS and primary progressive MS were examined for Th40 cell levels in peripheral blood and, similar to our findings in autoimmune type 1 diabetes, the levels were significantly (p<0.0001) elevated compared to controls including healthy non-autoimmune subjects and another non-autoimmune chronic disease. Classically identified Tregs were at levels equivalent to non-autoimmune controls but the Th40/Treg ratio still predicted autoimmunity. The cohort displayed a wide range of HLA haplotypes including the GWAS identified predictive HLA-DRB1*1501 (DR2). However half the subjects did not carry DR2 and regardless of HLA haplotype, Th40 cells were expanded during disease. In RRMS Th40 cells demonstrated a limited TCR clonality. Mechanistically, Th40 cells demonstrated a wide array of response to CNS associated self-antigens that was dependent upon HLA haplotype. Th40 cells were predominantly memory phenotype producing IL-17 and IFNγ with a significant portion producing both inflammatory cytokines simultaneously suggesting an intermediary between Th1 and Th17 phenotypes.