Background/Purpose

Scleroderma is a rare autoimmune disease characterized by the accumulation of fibrotic tissue in multiple organs including the skin, gut and lungs. To date, the cause of this disease has not been identified and specific treatments are unavailable. SclGVHD in mice recapitulates many scleroderma manifestations and can be used to determine potential therapeutic pathways. Previously, we identified activation of the Interleukin-13 (IL-13) cytokine pathway in the skin of both murine sclGVHD and a subset of scleroderma patients characterized by an “inflammatory” gene expression signature.  We also showed that host mice lacking IL4RA, a functional subunit of IL-13 and IL-4 receptors, are protected from the cutaneous manifestations of sclGVHD. The purpose of this study is to define the mechanism that protects IL4RA-deficient mice from sclGVHD.

Methods

Splenocytes from B10.D2 mice were transferred into either BALB/c Rag2^-/- or BALB/c Rag2^-/-Il4ra^-/- hosts to induce sclGVHD.  Seven days after cell transfer the skin was processed for histopathology and scored blindly for inflammation. Subcutaneous lymph-nodes (sLN) were isolated, collagenase digested and analyzed by flow cytometry. sLN cells were also stimulated in vitro for 5h with LPS, PMA and ionomycin to analyze IL-10 production by intracellular cytokine staining. mRNA was extracted from skin and sLN and subjected to qRT-PCR. Student’s t-tests, with n=10-13 per group, were used to determine statistical significance.

Results

One week after cell transfer IL4RA-deficient mice lost significantly less weight than control sclGVHD mice (8.44% ± 4.25 of baseline body weight vs. 16.28% ± 3.68, p<0.0001) and displayed less skin inflammation as assessed by histopathologic score (1.50 ± 0.53 for BALB/c Rag2^-/- and 0.80 ± 0.42 for BALB/c Rag2^-/-Il4ra^-/- , p=0.0042). Despite reduced skin inflammation, the sLNs of BALB/c Rag2^-/-Il4ra^-/- mice showed significantly higher cellularity (8.7 ± 2.33 x10⁶ vs. 3.09 ± 1.23 x10⁶, p<0.0001), with elevated numbers of T cells, B cells and myeloid CD11b⁺Ly6C⁺ cells compared to BALB/c Rag2^-/- controls. Cells from these three populations also produced more IL10 than those isolated from control mice when stimulated ex vivo. In addition, among the CD4⁺ T-cells, Il4RA-deficient hosts had a significantly higher frequency of Foxp3⁺ regulatory T-cells (13.92% ± 1.95 vs. 6.82% ±1.40, p<0.0001). qRT-PCR analysis also revealed elevated Il10 transcripts in the sLNs of BALB/c Rag2^-/-Il4ra^-/-  hosts (p=0.0008). In contrast, no differences were observed in transcript levels of chemokines important for the homing of immune cells to sLNs, including ccl19 and cxcl13. 

Conclusion

IL4RA promotes sclGVHD early in the disease course by promoting infiltration of immune cells into the skin and suppressing the expansion of regulatory T-cells and IL-10 expression. Surprisingly, the sLNs of mutant mice contained more adaptive and innate immune cells. Additional data are needed to understand if this accumulation of cells in sLN of IL4RA-deficient mice is due to a defect in the pathways that control apoptosis, proliferation or the migration of activated cells from the sLN to the skin.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/attenuation-of-sclerodermatous-graft-versus-host-disease-sclgvhd-in-il4ra-receptor-deficient-mice/