Article Text

PDF

Clinical hepatology
OP06 Tim3 down-regulation renders CD4 effector cells less susceptible to T-reg control in patients with autoimmune hepatitis
  1. R Liberal,
  2. Y Ma,
  3. G Mieli-Vergani,
  4. M Longhi
  1. King's College Hospital, UK

Abstract

Introduction In autoimmune hepatitis (AIH), the extent of CD4 effector immune responses is associated with defective CD4posCD25pos 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 CD4posCD25neg effector cells were purified from PBMCs using immunomagnetic beads. CD25neg cells were further purified into Tim3pos and Tim3neg cell fractions and used as targets in co-culture experiments with T-regs. Target cell proliferation was assessed after 5-day culture by 3H-thymidine incorporation and expressed as mean cpm count.

Results Proliferation of unfractionated CD25neg cells (HS: 37 745±5015; AIH: 6160+714) was lower than that of Tim3neg (HS: 115 488±8348, p=0.001; AIH: 9659+1041, p=0.02) and higher than that of Tim3pos (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 CD25neg cells were used as targets; by 25% (p=0.14) and 23% (p=NS) when Tim3neg cells were the targets and by 62% (p=0.04) and 43% (p=0.03) when the targets were Tim3pos cells. Since Tim3pos cells produce higher levels of IFN-gamma than Tim3neg cells, we investigated the effect of IFN-gamma neutralisation on the ability of Tim3pos and Tim3neg cells to be regulated by T-regs. While treatment with anti-IFN-gamma neutralising antibodies did not change Tim3neg cell susceptibility to T-reg control, it decreased it in Tim3pos cells, inhibition of proliferation being 17% in HS and nil in AIH following T-reg addition.

Conclusion Compared to unfractionated CD25neg and Tim3pos cells, Tim3neg 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 Tim3pos cells suggests that IFN-gamma production is needed in order for these cells to be effectively regulated.

Statistics from Altmetric.com

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.