more picking at the problem.....
PORCINE CELLS ADHERE TO HUMAN FIBRONECTIN INDEPENDENTLY OF VLA-5:
IMPLICATIONS FOR PORCINE TO HUMAN XENOTRANSPLANTATION.
Purpose: Effective adhesive interactions between species will be critical to the successful use of bone marrow
transplantation for the induction of xenotransplantation tolerance. The _1 integrin class of adhesion molecules
mediates adhesion of lymphocytes to extracellular matrix (ECM) proteins, and has been implicated in the
engraftment and maturation of hematopoietic stem cells. We have compared the role of the integrin very late
antigen 5 (VLA-5) in human versus pig cell adhesion to the human ECM protein fibronectin (FN) and in in vitro
hematopoiesis.
Methods: PBMCs from human and miniature swine were isolated and flourochrome labeled. Labeled cells
were placed on tissue culture plates coated with human FN, and adhesion to plates was determined via
flouremeter recordings following serial washings. An anti-human VLA-5 antibody, SAM-1, determined via
immunprecipitation to be cross-reactive on pig and human VLA-5, was added to the assay to attempt blockade
of cell adhesion to FN. Using rabbit complement, cells bearing the VLA-5 epitope recognized by SAM-1 were
then purged from the peripheral blood cell preparations before performing the adhesion assay. To further
investigate the functional effect of VLA-5 blockade within the extracellular matrix milieu, long term bone marrow
cultures (LTBMC) were established in the presence of anti-VLA-5 versus control antibody in both species.
Results: Porcine and human PBMC both adhered to human FN. Adhesion of human cells to FN was blocked
by anti-VLA-5 monoclonal antibody SAM-1. Adhesion of pig cells to FN was not blocked by anti-VLA-5 mAb
SAM-1. Complement-mediated purging of VLA-5- expressing cells ablated specific binding of human cells to
fibronectin, but porcine cells lacking VLA-5 retained the ability to adhere to human FN. Antibodies directed
against VLA-5 impaired in vitro human hematopoiesis but had no inhibitory effect on porcine LTBMC.
Conclusion: Porcine and human cells can use different molecules to adhere to fibronectin. Adhesion to FN is
VLA-5-dependent in human but not in pig. Human hematopoiesis appears to be dependent on this interaction,
but porcine hematopoiesis may not be. Optimization of porcine interactions with human FN may be critical for
successful pig to human xenogeneic chimerism and tolerance induction.
P. Theodore, A. Simon, R Sackstein, M. Sykes. Massachusetts General Hospital/Harvard Medical School. Boston,
MA 02129 |
