Contributions
Abstract: P1085
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Recent studies suggested that neutrophils may play an important role in MS and EAE pathogenesis as they seem to be involved in blood barrier breakdown and in shaping patterns of neuroinflammation. Programmed death (PD-1) receptor is involved in peripheral tolerance and in immune escape mechanisms during chronic inflammation. Its stimulation delivers inhibitory signal especially to activated T and B cells, contributing in the balance between immunotolerance and immunopathology. Two PD-1 ligands have been described, PD-L1 and PD-L2 that are expressed on a variety of immune cells. Recent evidences indicate that PD-L1 is expressed on neutrophils. This expression seems to correlate with disease activity in systemic lupus erythematosus (SLE). In addition to this, there are few evidences that PD-1-pathway have a role in MS and EAE disease activity and progression. However, frequency and role of PD-L1 and PD-L2 expressing neutrophils have not been explored in EAE. Therefore, our aim was to investigate the expression of PD-1-pathway on CNS infiltrating neutrophils in EAE.
Methods: EAE was induced with 35-55-MOG in 8 weeks C57/Bl6 mice (n=11). Mice were sacrificed at different time points: 15(n=4), 20(n=4) and 27(n=3) days post immunization (dpi). CNS infiltrating cells where isolated by percoll density gradient centrifugation protocol, using multiparametric flow-cytometry and then analysed. Results were compared to 3 control mice.
Results: We compared the percentage of neutrophils (LyG6+) on the total amount of CD45+ CNS infiltrating cells. We found out that this percentage was higher in EAE mice compared to controls (Mann Whitney p=0.016). We found no significant expression of PD-1 on neutrophils. PD-L1 and PD-L2 were significantly more expressed in EAE compared to controls (Mann-Whitney, p=0.010 p=0.016). Post-hoc analysis showed that PD-L1 was higher in EAE at all time points (Mann Whitney 15 dpi p=0.034; 20 dpi p=0.034; 27 dpi p=0.05). No differences were found between time points. Differently, PD-L2 expression was significantly increased only at 15 and 20 dpi (p=0.34).
Conclusions: The percentage of PD-L1 and PD-L2 expressing neutrophils is increased in EAE model. Consistent to what was suggested for SLE, it may serve as negative feedback mechanism downregulating active lymphocytes during CNS autoimmune aggression. PD-L2 expression seems to decrease after 20 dpi; this might be due to a lower neuroinflammatory activity in the later phases of disease
Disclosure: Author declare no conflict of interest
Abstract: P1085
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Immunology
Introduction: Recent studies suggested that neutrophils may play an important role in MS and EAE pathogenesis as they seem to be involved in blood barrier breakdown and in shaping patterns of neuroinflammation. Programmed death (PD-1) receptor is involved in peripheral tolerance and in immune escape mechanisms during chronic inflammation. Its stimulation delivers inhibitory signal especially to activated T and B cells, contributing in the balance between immunotolerance and immunopathology. Two PD-1 ligands have been described, PD-L1 and PD-L2 that are expressed on a variety of immune cells. Recent evidences indicate that PD-L1 is expressed on neutrophils. This expression seems to correlate with disease activity in systemic lupus erythematosus (SLE). In addition to this, there are few evidences that PD-1-pathway have a role in MS and EAE disease activity and progression. However, frequency and role of PD-L1 and PD-L2 expressing neutrophils have not been explored in EAE. Therefore, our aim was to investigate the expression of PD-1-pathway on CNS infiltrating neutrophils in EAE.
Methods: EAE was induced with 35-55-MOG in 8 weeks C57/Bl6 mice (n=11). Mice were sacrificed at different time points: 15(n=4), 20(n=4) and 27(n=3) days post immunization (dpi). CNS infiltrating cells where isolated by percoll density gradient centrifugation protocol, using multiparametric flow-cytometry and then analysed. Results were compared to 3 control mice.
Results: We compared the percentage of neutrophils (LyG6+) on the total amount of CD45+ CNS infiltrating cells. We found out that this percentage was higher in EAE mice compared to controls (Mann Whitney p=0.016). We found no significant expression of PD-1 on neutrophils. PD-L1 and PD-L2 were significantly more expressed in EAE compared to controls (Mann-Whitney, p=0.010 p=0.016). Post-hoc analysis showed that PD-L1 was higher in EAE at all time points (Mann Whitney 15 dpi p=0.034; 20 dpi p=0.034; 27 dpi p=0.05). No differences were found between time points. Differently, PD-L2 expression was significantly increased only at 15 and 20 dpi (p=0.34).
Conclusions: The percentage of PD-L1 and PD-L2 expressing neutrophils is increased in EAE model. Consistent to what was suggested for SLE, it may serve as negative feedback mechanism downregulating active lymphocytes during CNS autoimmune aggression. PD-L2 expression seems to decrease after 20 dpi; this might be due to a lower neuroinflammatory activity in the later phases of disease
Disclosure: Author declare no conflict of interest