Session Time: 3:15pm-4:00pm
Presentation Time: 3:30pm-4:00pm
*Purpose: B cells expanded in vitro via TLR9 agonist CpG and activated by LPS, PMA and ionomycin have been previously denoted “TLR-Bregs” by our team. These TLR-Bregs have shown the capacity to inhibit the proliferation of T cells in in vitro MLRs and to prolong survival of allografts in vivo when administered to B cell deficient mice. Here, we explore the mechanism of their suppressive function in vivo.
*Methods: TLR-Bregs were expanded in vitro from naive C57BL/6 B cells (B6 TLR-Bregs) or B cells from transgenic OB1 mice whose B cell receptor is OVA-specific (OB1 TLR-Bregs). Skin transplant experiments utilized OVA-expressing B6 transgenic mice as donors and naive B6 mice as recipients. CFSE-labeled OVA-specific TCR transgenic (OT-II) CD4 T cells were adoptively transferred with or without B6 TLR-Bregs or OB1 TLR-Bregs. Cells from draining lymph nodes (DLN), non-draining lymph nodes (NDLN), and spleen were harvested and examined by flow cytometry.
*Results: Flow cytometry revealed T cell proliferation concentrated in the DLN, but not the NDLN or spleen. The average percentage of proliferated CD4+T cells was 80% when no B cells were given and 83% with 5 million (M) naive B6 B cells. Recipients given a dose of 5M or 10M B6 TLR-Bregs showed significantly less proliferation of CD4+T cells (50%, p<0.05), but no change with 3M B6 TLR-Bregs (90%). Furthermore, the average percentage of proliferated CD4+T cells was even lower when recipients were given 3M OB1 TLR-Bregs (27%, p<0.001) and 5M OB1 TLR-Bregs (15%, p<0.01) in comparison to the same dose of B6 TLR-Bregs.
*Conclusions: A model was established that allows specific tracking of donor specific Bregs and of their interactions with donor specific T cells. When compared to naive B6 TLR-Bregs, the OVA-specific TLR-Bregs showed stronger suppression of OVA-specific CD4+T cell proliferation against OVA skin grafts. We hypothesize that the increased precursor frequency of OVA-specific suppressive Bregs from OB1 mice explains this difference in the ability to prevent skin graft rejection. Alterations in the phenotype, gene expression and function of the responding T cells induced by Bregs is currently under study.
To cite this abstract in AMA style:Huai G, Lee KM, Fu Q, Deng K, Feeney NJ, Leguern C, Tanimine N, Rickert CG, Deng S, Markmann JF. Ex Vivo Generated Regulatory B Cells Can Suppress Donor-Specific CD4 T Cells Proliferation In Vivo [abstract]. Am J Transplant. 2020; 20 (suppl 3). https://atcmeetingabstracts.com/abstract/ex-vivo-generated-regulatory-b-cells-can-suppress-donor-specific-cd4-t-cells-proliferation-in-vivo/. Accessed May 9, 2021.
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