Cells were labeled with 5 μM carboxyfluorescein diacetate succinimidyl ester (CFSE) for 10 min at 37 °C. 105 cells were cultured in the absence or presence of plate-bound antibodies against CD3 and CD28 (1 μg/ml) for 72 h. Cells were stained with antibodies against CD4, CD8 and CD25 and analyzed by FACS in duplicates. T cells from spleens and lymph nodes from Vav1AA/AA and C57BL/6 WT mice were purified as described for the T

cell activation analysis. The one-way MLR was performed in 96-well plates using irradiated BALB/c splenocytes as allogeneic stimulators. Different numbers of purified responder T cells (1 × 105, 2 × 105, 4 × 105) were mixed with different numbers of stimulator splenocytes (2 × 105, 4 × 105, 8 × 105) and incubated for 4 days at 37 °C in a humidified hypoxia-inducible factor pathway incubator. After a 5 hour exposure to 3H thymidine, proliferation was measured in a Betaplate Counter (Wallac). Data are shown as mean values ± SD of triplicates. Single cell suspensions were prepared from spleens of Vav1AA/AA mice and WT littermate controls. After

red blood cell lysis with ACK buffer (Sigma-Aldrich), cells were labeled with 2 μM carboxyfluorescein diacetate succinimidyl FDA-approved Drug Library research buy ester (CFSE) for 10 min at 37 °C. SCID-beige recipient mice were injected i.v. with 20 × 106 unfractionated WT splenocytes or 40–60 × 106 spleen cells from Vav1AA/AA donors, respectively, to transfer 7 × 106 T cells (as determined by anti-CD3 staining). Four days after transfer, cell suspensions were prepared from individual SCID recipient spleens and T-cell recovery was analyzed by four-color flow cytometry, CFSE, anti-CD4-PE, anti-CD8-PerCP and anti CD3-APC. Flow cytometry data were acquired on a FACScalibur (BD Biosciences) using CellQuest software. Data were analyzed with FlowJo software (Treestar, San Carlos, CA, USA).

Estimates of CD4+ and CD8+ T-cell numbers per recipient spleen were calculated as the product of the total number of viable spleen Ceramide glucosyltransferase cells (hemocytometer count, trypan blue exclusion) and the percentage of CD3+ CD4+ and CD3+ CD8+ spleen cells within the live lymphocyte forward/side scatter gate. The percentage of CD4+ or CD8+ T cells that had undergone a certain number of cell cycles was derived from marker settings on CFSE histograms. For cell cycle distribution plots, the arithmetic means and SD of all individual data per recipient group are shown. Heterotopic heart transplantation was performed as described by [24] using aseptic surgery techniques. Briefly, animals were anesthetized using isoflurane. Following heparinization of the donor mouse, the chest was opened and the heart rapidly cooled with ice cold saline. The aorta and pulmonary artery were ligated and divided and the donor heart was stored in ice cold saline.