OP06 Tim3 down-regulation renders CD4 effector cells less susceptible to T-reg control in patients with autoimmune hepatitis. (16th November 2010)

• Record Type: Journal Article
• Authors: Liberal, R; Ma, Y; Mieli-Vergani, G; Longhi, M
• Is Part Of: Gut. Volume 59(2010)Supplement 2
• Page Start: A3
• Page End: A3
• Publication Date: 2010-11-16
• Subjects: Gastroenterology -- Periodicals; 616.33
• DOI: 10.1136/gut.2010.223362.6
• Languages: English
• ISSNs: 0017-5749

Abstract

Abstract : Introduction: In autoimmune hepatitis (AIH), the extent of CD4 effector immune responses is associated with defective CD4 pos CD25 pos regulatory T-cells (T-regs). Engagement of T-cell-immunoglobulin-and-mucin-domain-3 (Tim3) on Th1-cells by galectin-9, expressed by T-regs, induces Th1-cell apoptosis. In AIH, Tim3 is down-regulated on CD4 effector cells. Whether the reduced Tim3 expression renders CD4 T-cells less susceptible to T-reg control is unknown. Aim: To evaluate whether Tim3 expression is associated with the ability of CD4 effector cells to be regulated by T-regs in AIH. Method: 18 ANA/SMA+ patients (median age: 14.9 years, 11 females) and 6 healthy subjects (HS, median age: 28.4, 5 females) were studied. T-regs and CD4 pos CD25 neg effector cells were purified from PBMCs using immunomagnetic beads. CD25 neg cells were further purified into Tim3 pos and Tim3 neg cell fractions and used as targets in co-culture experiments with T-regs. Target cell proliferation was assessed after 5-day culture by 3 H-thymidine incorporation and expressed as mean cpm count. Results: Proliferation of unfractionated CD25 neg cells (HS: 37 745±5015; AIH: 6160+714) was lower than that of Tim3 neg (HS: 115 488±8348, p=0.001; AIH: 9659+1041, p=0.02) and higher than that of Tim3 pos (HS: 29 382±2323, p=0.03; AIH: 4604±1177, p=0.004) cells. Addition of T-regs reduced cell proliferation by 51% (P<0.001) in HS and by 26% (p=NS) in AIH when unfractionated CD25 neg cells were used as targets; by 25% (p=0.14) and 23% (p=NS) when Tim3 neg cells were the targets and by 62% (p=0.04) and 43% (p=0.03) when the targets were Tim3 pos cells. Since Tim3 pos cells produce higher levels of IFN-gamma than Tim3 neg cells, we investigated the effect of IFN-gamma neutralisation on the ability of Tim3 pos and Tim3 neg cells to be regulated by T-regs. While treatment with anti-IFN-gamma neutralising antibodies did not change Tim3 neg cell susceptibility to T-reg control, it decreased it in Tim3 pos cells, inhibition of proliferation being 17% in HS and nil in AIH following T-reg addition. Conclusion: Compared to unfractionated CD25 neg and Tim3 pos cells, Tim3 neg effectors display higher ability to proliferate and are less susceptible to T-reg control especially in AIH. Down-regulation of Tim3 renders CD4 effectors less amenable to immune regulation and therefore more likely to inflict and perpetuate liver damage. The decreased ability of T-regs to suppress proliferation of anti-IFN-gamma-treated Tim3 pos cells suggests that IFN-gamma production is needed in order for these cells to be effectively regulated.