POS1356 PERSISTENCE OF TFH CELLS AFTER RITUXIMAB IS ASSOCIATED WITH IGG4-RELATED DISEASE RELAPSE

Background:

Clinical improvement after B-cell depletion with rituxmab suggests a prominent pathogenic role of B-lymphcytes in IgG4-related disease (IgG4-RD). IgG4-RD, however, relapses in most cases together with re-expansion of clonally divergent plasmablasts indicating that treatment with rituximab does not completely abrogates T follicular helper (Tfh)-cells dependent germinal center reactions leading to de-novo plasmablast differentiation.

Objectives:

In the present work we aim to study the effects of B-cell depletion therapy with rituximab on circulating Tfh cells and on the levels of CXCL13 - a chemotactic factor for B-lymphocytes produced by Tfh cells - in patients with IgG4-RD.

Methods:

Thirty patients with IgG4-RD, diagnosed according to the “Consensus Statement on the Pathology of IgG4-RD” and fulfilling the “2019 ACR/EULAR Classification Criteria” were included in the present study. Ten patients with relapsing disease were treated with the anti-CD20 monoclonal antibody rituximab (two 1g infuxions 15 days apart). Peripheral blood mononuclear cells and serum were collected before rituximab and three months after infusion. Tfh cells subsets in the peripheral blood were measured by flow cytometry and CXCL13 plasma levels were measured by ELISA assay.

Results:

No changes in total Tfh cells and Tfh cells subsets were observed three months after rituximab neither in absolute counts nor in percentage of CD4+ T cells. In particular, no difference in Tfh1, Tfh2, Tfh17, T follicular regulatory and highly functional Tfh cells counts was observed before and after treatment. The serum level of CXCL13 was significantly higher in active untreated IgG4-RD patients compared to healthy controls (151.94 pg/ml vs 66.98 pg/ml, p value = 0.0026), but was not affected by rituximab treatment (p value = 0.41).

Conclusion:

In relapsing patients with IgG4-RD rituximab does not affect circulating Tfh cells numbers and serum levels of CXCL13. Persistence of Tfh cells after rituximab and reconstitution of germinal center reactions likely drives IgG4-RD flare.

References:

[1]Lanzillotta M, Mancuso G, Della-Torre E. Advances in the diagnosis and management of IgG4 related disease. BMJ. 2020 Jun 16;369:m1067. doi: 10.1136/bmj.m1067. PMID: 32546500.

[2]Lanzillotta M, Della-Torre E, Stone JH. Roles of Plasmablasts and B Cells in IgG4-Related Disease: Implications for Therapy and Early Treatment Outcomes. Curr Top Microbiol Immunol. 2017;401:85-92. doi: 10.1007/82_2016_58. PMID: 28091934.

[3]Campochiaro C, Ramirez GA, Bozzolo EP, Lanzillotta M, Berti A, Baldissera E, Dagna L, Praderio L, Scotti R, Tresoldi M, Roveri L, Mariani A, Balzano G, Castoldi R, Doglioni C, Sabbadini MG, Della-Torre E. IgG4-related disease in Italy: clinical features and outcomes of a large cohort of patients. Scand J Rheumatol. 2016;45(2):135-45. doi: 10.3109/03009742.2015.1055796. Epub 2015 Sep 23. PMID: 26398142.

[4]Mattoo H, Mahajan VS, Della-Torre E, Sekigami Y, Carruthers M, Wallace ZS, Deshpande V, Stone JH, Pillai S. De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease. J Allergy Clin Immunol. 2014 Sep;134(3):679-87. doi: 10.1016/j.jaci.2014.03.034. Epub 2014 May 6. PMID: 24815737; PMCID: PMC4149918.

Disclosure of Interests:

None declared

Key role of macrophages in tolerance induction via T regulatory type 1 (Tr1) cells

T regulatory type 1 (Tr1) cells are a class of regulatory T cells (T_regs ) participating in peripheral tolerance, hence the rationale behind their testing in clinical trials in different disease settings. One of their applications is tolerance induction to allogeneic islets for long-term diabetes-free survival. Currently the cellular and molecular mechanisms that promote Tr1-cell induction in vivo remain poorly understood. We employed a mouse model of transplant tolerance where treatment with granulocyte colony-stimulating factor (G-CSF)/rapamycin induces permanent engraftment of allogeneic pancreatic islets in C57BL/6 mice via Tr1 cells. The innate composition of graft and spleen cells in tolerant mice was analyzed by flow cytometry. Graft phagocytic cells were co-cultured with CD4⁺ T cells in vitro to test their ability to induce Tr1-cell induction. Graft phagocytic cells were depleted in vivo at different time-points during G-CSF/rapamycin treatment, to identify their role in Tr1-cell induction and consequently in graft survival. In the spleen, the site of Tr1-cell induction, no differences in the frequencies of macrophages or dendritic cells (DC) were observed. In the graft, the site of antigen uptake, a high proportion of macrophages and not DC was detected in tolerant but not in rejecting mice. Graft-infiltrating macrophages of G-CSF/rapamycin-treated mice had an M2 phenotype, characterized by higher CD206 expression and interleukin (IL)-10 production, whereas splenic macrophages only had an increased CD206 expression. Graft-infiltrating cells from G-CSF/rapamycin-treated mice-induced Tr1-cell expansion in vitro. Furthermore, Tr1-cell induction was perturbed upon in-vivo depletion of phagocytic cells, early and not late during treatment, leading to graft loss suggesting that macrophages play a key role in tolerance induction mediated by Tr1 cells. Taken together, in this mouse model of Tr1-cell induced tolerance to allogeneic islets, M2 macrophages infiltrating the graft upon G-CSF/rapamycin treatment are key for Tr1-cell induction. This work provides mechanistic insight into pharmacologically induced Tr1-cell expansion in vivo in this stringent model of allogeneic transplantation.

Experimental colitis in IL-10-deficient mice ameliorates in the absence of PTPN22

Interleukin (IL)-10 plays a key role in controlling intestinal inflammation. IL-10-deficient mice and patients with mutations in IL-10 or its receptor, IL-10R, show increased susceptibility to inflammatory bowel diseases (IBD). Protein tyrosine phosphatase, non-receptor type 22 (PTPN22) controls immune cell activation and the equilibrium between regulatory and effector T cells, playing an important role in controlling immune homoeostasis of the gut. Here, we examined the role of PTPN22 in intestinal inflammation of IL-10-deficient (IL-10^-/- ) mice. We crossed IL-10^-/- mice with PTPN22^-/- mice to generate PTPN22^-/- IL-10^-/- double knock-out mice and induced colitis with dextran sodium sulphate (DSS). In line with previous reports, DSS-induced acute and chronic colitis was exacerbated in IL-10^-/- mice compared to wild-type (WT) controls. However, PTPN22^-/- IL-10^-/- double knock-out mice developed milder disease compared to IL-10^-/- mice. IL-17-promoting innate cytokines and T helper type 17 (Th17) cells were markedly increased in PTPN22^-/- IL-10^-/- mice, but did not provide a protctive function. CXCL1/KC was also increased in PTPN22^-/- IL-10^-/- mice, but therapeutic injection of CXCL1/KC in IL-10^-/- mice did not ameliorate colitis. These results show that PTPN22 promotes intestinal inflammation in IL-10-deficient mice, suggesting that therapeutic targeting of PTPN22 might be beneficial in patients with IBD and mutations in IL-10 and IL-10R.

The protein tyrosine phosphatase PTPN22 controls forkhead box protein 3 T regulatory cell induction but is dispensable for T helper type 1 cell polarization

Protein tyrosine phosphatases (PTPs) regulate T cell receptor (TCR) signalling and thus have a role in T cell differentiation. Here we tested whether the autoimmune predisposing gene PTPN22 encoding for a PTP that inhibits TCR signalling affects the generation of forkhead box protein 3 (FoxP3)(+) T regulatory (Treg ) cells and T helper type 1 (Th1) cells. Murine CD4(+) T cells isolated from Ptpn22 knock-out (Ptpn22(KO) ) mice cultured in Treg cell polarizing conditions showed increased sensitivity to TCR activation compared to wild-type (WT) cells, and subsequently reduced FoxP3 expression at optimal-to-high levels of activation. However, at lower levels of TCR activation, Ptpn22(KO) CD4(+) T cells showed enhanced expression of FoxP3. Similar experiments in humans revealed that at optimal levels of TCR activation PTPN22 knock-down by specific oligonucleotides compromises the differentiation of naive CD4(+) T cells into Treg cells. Notably, in vivo Treg cell conversion experiments in mice showed delayed kinetic but overall increased frequency and number of Treg cells in the absence of Ptpn22. In contrast, the in vitro and in vivo generation of Th1 cells was comparable between WT and Ptpn22(KO) mice, thus suggesting PTPN22 as a FoxP3-specific regulating factor. Together, these results propose PTPN22 as a key factor in setting the proper threshold for FoxP3(+) Treg cell differentiation.

Subcutaneous insulin B:9-23/IFA immunisation induces Tregs that control late-stage prediabetes in NOD mice through IL-10 and IFNgamma

AIMS/HYPOTHESIS

Subcutaneous immunisation with the 9-23 amino acid region of the insulin B chain (B:9-23) in incomplete Freund's adjuvant (IFA) can protect the majority of 4- to 6-week-old prediabetic NOD mice and is currently in clinical trials. Here we analysed the effect of B:9-23/IFA immunisation at later stages of the disease and the underlying mechanisms.

METHODS

NOD mice were immunised once s.c. with B:9-23/IFA at 5 or 9 weeks of age, or when blood glucose reached 10 mmol/l or higher. Diabetes incidence was followed in addition to variables such as regulatory T cell (Treg) induction, cytokine production (analysed by Elispot) and emergence of pathogenic CD8(+)/NRP-V7(+) cells.

RESULTS

A single B:9-23/IFA immunisation protected the majority of NOD mice at advanced stages of insulitis, but not after blood glucose reached 13.9 mmol/l. It increased Treg numbers and lost its protective effect after IFNgamma or IL-10 neutralisation, but not in the absence of IL-4. CD4(+)CD25(+) and to a lesser extent IFNgamma-producing cells from mice protected by B:9-23/IFA induced tolerance upon transfer into new NOD animals, indicating that a dominant Treg-mediated effect was operational. Reduced numbers of CD8(+)/NRP-V7(+) memory T cells coincided with protection from the disease.

CONCLUSIONS/INTERPRETATION

Protection from diabetes after B:9-23/IFA immunisation cannot be achieved once diabetes is fully established, but can be achieved at most prediabetic stages of the disease. Protection is mediated by Tregs that require IFNgamma and IL-10. These findings should provide important guidance for ongoing human trials, especially for the development of suitable T cell biomarkers.