UC Merced

Systemic lupus erythematosus is characterized by robust self-reactive T and B cells leading to lymphoproliferation, nephritis, and inflammation. It remains unknown if T cells in SLE undergo exhaustion programming. Exhaustion is a dysfunctional mechanism in high antigen environments that leads to inhibition of T cell activation as identified in infection and cancer. B cells within SLE may become activated within germinal centers through their interaction with CXCR5+CD8 T cells. CXCR5+CD8 T cells are known to contribute to B cell activation and plasma cell differentiation while expressing PD-1 in germinal centers of peripheral organs and ectopic germinal center environments. These T cells correlate with autoimmune disease upregulation through B cell interactions and autoantibody production. Scientific interest in CXCR5+CD8 T cells has expanded and shown good prognostic value against infection and cancer. We were interested in understanding CXCR5+CD8 T cell dynamics compared to CXCR5-CD8, CXCR5+ and CXCR5- CD4 T cells in autoimmune disease. CXCR5+CD8 and CXCR5- CD8 T cells expand in SLE as disease progresses from 2-6 months in males and females. CXCR5+ CD8 T cells were not high contributors to TNFα production which has been identified as a promoter of SLE but produced considerable amounts of IFNγ. CXCR5- CD8 T cells produced both TNFα and IFNγ. Next, we investigated CXCR5+CD8 T cell functionality through inhibitory marker expression (PD-1, Tim3, CTLA4, and Lag3) in MRL/lpr mice compared to MRL/MpJ controls. Our results showed increases in inhibitory marker expression of Tim3 and Lag3 programming in CXCR5+ and CXCR5- CD8 and CD4 T cells of both males and females. These results are an indication of CD8 and CD4 T cell exhaustion programming in severe autoimmunity that has not been previously established. Further research is needed to verify self-reactivity and if these are bystander cells. High antigen tumor microenvironments increase the likelihood of inhibitory receptor activation on T cells. Checkpoint blockade therapy has been developed to combat the inhibition of activated T cells in tumor microenvironments, but immunotherapies also lead to the development of immune-mediated adverse events or immune-related adverse events. IMAEs resemble over 80 different autoimmune diseases in 70-90% of checkpoint blockade patients. We set out to develop a novel mouse model for studying IMAE development and to view differences in IMAE development following anti-PD-1 therapy in mice with genetic predisposition to mild and severe autoimmunity. To this end, we investigated anti-PD-1 therapy dynamics across 8-weeks in B6, MRL/MpJ and MRL/lpr mice with blood and serum collection, weights, urinalysis, protein expression and organ histology. MRL/MpJ mice develop mild autoimmunity at 2 years of age, while the related MRL/lpr mice develop autoimmunity at 8 weeks of age, representing two genetic backgrounds that predisposes mice to “mild” and “severe” autoimmunity. Our results revealed potential blood and serum biomarker identification for IMAE development in red blood cell count and dsDNA autoantibody production in B6 and MRL/MpJ mice. Peripheral blood unveiled an increased population of CD19+CD138 plasma cell in severely autoimmune male and female mice that has yet to be fully described in checkpoint blockade literature. Consistent with patient data there was increased naïve and memory T and B cell populations with decreased effectors following anti-PD-1 blockade in MRL/MpJ and MRL/lpr mice. Differences between severely autoimmune male and females arose after treatment giving a new understanding of autoimmune regulation between sexes. MRL/lpr males decreased Tim3 inhibitory marker expression, whereas MRL/lpr females increased this expression and increased the expression for short-lived effector through KLRG1 after anti-PD-1 therapy. This may explain why males have increased response to checkpoint therapy compared to females. Lastly, we identified tumor development after anti-PD-1 treatment was given in 25% of B6, MRL/MpJ and MRL/lpr female mice, but not males. Tumor formation after checkpoint blockade therapy has not been previously described in mice, possibly due to a lack of histological analysis beyond tumor resection. In conclusion, our results indicate a better prognosis for males compared to females and severely autoimmune MRL/lpr mice compared to B6 and MRL/MpJ mice after anti-PD-1 therapy. Importantly, our data suggests that female MRL mice may be a model to test for IMAE with respect to complete blood counts, autoantibody formation and tumor development.