The graft was implanted with
end-to-side anastomoses between the donor right brachiocephalic trunk and the recipient aorta and the donor right pulmonary artery to the recipient vena cava. Grafts were monitored by daily palpation and were considered rejected upon cessation of palpable ventricular contractions. Genotypes of all animals have been confirmed at the end of the study. Cardiac allografts and recipient hearts were cut transversally and fixed in 4% buffered formalin for histological evaluation. Fixed tissues were processed and embedded in paraffin according to standard procedures. Sections were stained with hematoxylin and eosin and Van Gieson for elastic fibers for light microscopic examination. Acute rejections were graded on scale 0 R (no rejection) to 3 R (severe selleckchem acute cellular rejection) [25]. Cardiac allografts were analyzed immunohistochemically.
Standard procedures were applied using mAbs anti-alpha smooth muscle actin (αSMA, clone 1A4, Dako-Cytomation, Glostrup, Denmark), anti-CD3 (clone CD3-12, Serotec Ltd, Oxford, UK), anti-CD45R (clone RA3-6B2, Serotec Ltd) and the streptavidin–biotin–peroxidase complex technique. Spleen tissue served as positive control sample. Negative immunohistochemical staining controls were obtained by replacing the primary antibodies with antibody isotype controls (Zymed Laboratories, Inc., Vincristine manufacturer San Francisco, CA, USA). Purified CD4+ T cells from BALB/c spleens were incubated with serum from naive or transplanted wildtype or Vav1AA/AA mice for 30 min on ice. Alloreactive antibodies were detected by FACS using FITC-conjugated anti-IgM and anti-IgG antibodies. Secreted levels of IL-2 in supernatants from stimulated cells were analyzed by MYO10 ELISA according to manufacturer’s instructions (DuoSet ELISA kit, R&D Systems, Minneapolis, MN, USA). Absorbance at 450 nm was measured using a SpectraMAX 190 ELISA reader (Molecular Devices). Data were expressed as mean ± standard deviation (SD). Statistical significance was determined using a two-tailed, unpaired Student’s T-test. (*p < 0.05, **p < 0.01, n.s. not significant). For the heart allograft transplantation model,
significance was determined by Kaplan–Meier survival curves and Mantel–Cox test. To address the contribution of the GEF function of Vav1 for T cell activation in the context of allograft rejection, we made use of knock-in mice which carry a mutation in the DH domain of Vav1 (Vav1AA/AA). These mice express a mutated Vav1 which cannot activate Rac but has intact GEF-independent functions such as TCR-induced Ca2+ flux [20]. In order to determine if disruption of Vav1 GEF activity alone affects T cell proliferation and activation, purified T cells from Vav1AA/AA and wild-type (WT) control mice were labeled with the fluorescent dye CFSE and stimulated on plates coated with antibodies against CD3 and CD28. After 3 days, proliferation and activation were assessed by flow cytometry.