Adoptive transfer of B cells transfers tolerance.

<p>Cells were sorted by FACS Aria <b>(sorting strategy displayed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119686#pone.0119686.s003" target="_blank">S3D and E Fig.</a>)</b> from the spleen of tolerant rats (>100 days after the graft) that had received a transfer of splenocytes from a previously tolerant recipient and adoptively transferred to sub-lethally irradiated recipients the day before the transplant. <b>(A)</b> B cells (CD45RA⁺, n = 3), T cells (TCR⁺, n = 4), CD8⁺ Tregs (CD8⁺CD45RC^low, n = 2), pDCs (mAb 85C7⁺ n = 3) Groups are compared with each other and to irradiated animals transferred with naive splenocytes (naive splenocytes, n = 5) by Log-rank (Mantel-Cox) Test <i>p</i> <0.05*; p<0.01**; p<0.001***. <b>(B)</b> Wild type (WT) and B cell-deficient <i>Igm</i> knockout (KO) rats were treated with AAV-FGL2 (n = 8 and 3, respectively), AAV-null (n = 5) or untreated (NT, n = 3), and analyzed for graft survival. <b>(C)</b> Splenocytes from adoptively-transferred tolerant rats were depleted in CD45RA⁺ B cells (CD45RA⁻ cells) or not (splenocytes) and transferred to new irradiated recipients. Log-rank (Mantel-Cox) Test p<0.01**. <b>(D) Left:</b> A fraction of the transferred tolerogenic CD45RA⁺ B cells was tested for inhibition of CFSE-labeled CD4⁺CD25⁻ T cell proliferation in response to allogeneic LEW.1W cDCs, pDCs (stimulator/effector ratio of 1:4) or anti-CD3 at day 6 of culture. Shaded grey: naive CD45RA⁺ B cells n = 3, black line: tolerogenic CD45RA⁺ B cells n = 4. <b>Right</b>: Representative histogram of one proliferation assay of CD4⁺CD25⁻ T cells with allogeneic pDCs and CD45RA⁺ B cells from naive (shaded grey) or splenocyte-transferred tolerant rats (black line). <b>(E)</b> Graft infiltrating cells were analyzed for the presence of CD45RA⁺ cells in graft of rats transferred with B cells, at days 100 after the graft, as compared with syngeneic grafts (n = 3).</p

Splenocytes from AAVFGL2-treated rats with long-term surviving grafts transfer donor alloantigen-specific long-term graft survival in an iterative manner.

<p>Splenocytes from long-term AAV-FGL2-treated recipients were injected <i>i</i>.<i>v</i>. into sub-lethally irradiated recipients (LEW.1A) the day before heart allotransplantation (LEW.1W). Graft survival was evaluated by palpation through the abdominal wall. Total splenocytes (1x10⁸ cells) from long-term (≥120 days) AAV-FGL2-treated rats were adoptively transferred (1^st-transferred, n = 5), and then total splenocytes (10⁸ cells) were iteratively transferred to 2^nd- (n = 6), 3rd (n = 4), 4^th (n = 3), 5^th (n = 3) and 6^th (n = 3) LEW.1A recipients receiving LEW.1W hearts. Third-party grafts were from Brown-Norway origin and adoptive transfer of splenocytes from LEW.1W-transplanted animals did not inhibit acute rejection (third party, n = 3, performed in animals that received a second adoptive transfer). Splenocytes from naive non-transplanted rats did not inhibit acute rejection (naive splenocytes, n = 5) and non-irradiated non-transferred recipients (no treatment, n = 6) also showed acute rejection. Irradiation alone without cell transfer delays graft survival but does not prevent graft from rejection (irradiated, n = 5). All groups were compared to irradiated animals transferred with naive splenocytes by Log-rank (Mantel-Cox) Test (<i>p value</i> ***<0.001).</p

Over-expression of FGL2 <i>in vivo</i> prolongs cardiac allograft survival.

<p><b>(A)</b> Cardiac graft recipients received intravenously 3x10¹²vector genomes/kg of AAV-FGL2 (▲ n = 8), or non coding AAV (▼ n = 5, 2 different experiments), and received a heterotopic transplant 30 days later. Graft survival was evaluated by palpation through the abdominal wall. Log-rank (Mantel-Cox) test ***<i>p<0</i>.<i>001</i> for AAV-FGL2 vs. AAV null controls. <b>(B)</b> Left: Relative proportion of dividing CD4⁺CD25⁻ T cells at day 6 in the presence of different concentrations of recombinant human FGL2-GST was evaluated by CFSE dilution by gating first on DAPI^- live cells and then on TCR⁺CD4⁺ cells <b>(<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119686#pone.0119686.s002" target="_blank">S2B Fig.</a>).</b> The negative control was purified rat IgG at 10 μg/ml (n = 4, ** <i>p</i><0.01). Right: Representative histogram of relative proportion of dividing CD4⁺T cell in the presence of 10μg/ml FGL2-GST protein (black line) or IgG control (grey).</p

Alloantibody production was suppressed after AAV-FGL2 treatment and adoptive transfer of splenocytes.

<p>Sera were collected from naive rats, or at the moment of rejection from rats treated with AAV-control or AAV-FGL2 (rejecting at < 30 days or > 120 days after transplantation) or receiving adoptive transfers (> 120 days after transplantation). Levels of donor-specific IgG1, IgG2a, and IgG2b antibodies were evaluated by cytofluorimetry and normalized to serum from naive rats (MFI / MFI syngeneic). Two way Anova, Bonferroni post test <i>p value</i> * <0.5; ** <0.01; ***<0.001.</p