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Release of pig leukocytes and reduced human NK cell recruitment during ex vivo perfusion of HLA ‐E/human CD 46 double‐transgenic pig limbs with human blood
Abstract
Background
In pig‐to‐human xenotransplantation, interactions between human natural killer (
NK
) cells and porcine endothelial cells (
pEC
) are characterized by recruitment and cytotoxicity. Protection from xenogeneic
NK
cytotoxicity can be achieved in vitro by the expression of the non‐classical human leukocyte antigen‐E (
HLA
‐E) on
pEC
. Thus, the aim of this study was to analyze
NK
cell responses to vascularized xenografts using an ex vivo perfusion system of pig limbs with human blood.
Methods
Six pig forelimbs per group, respectively, stemming from either wild‐type (wt) or
HLA
‐E/
hCD
46 double‐transgenic (tg) animals, were perfused ex vivo with heparinized human blood for 12 hours. Blood samples were collected at defined time intervals, cell numbers counted, and peripheral blood mononuclear cells analyzed for phenotype by flow cytometry. Muscle biopsies were analyzed for
NK
cell infiltration. In vitro
NK
cytotoxicity assays were performed using
pEC
derived from wt and tg animals as target cells.
Results
Ex vivo, a strong reduction in circulating human
CD
45 leukocytes was observed after 60 minutes of xenoperfusion in both wt and tg limb groups.
NK
cell numbers dropped significantly. Within the first 10 minutes, the decrease in
NK
cells was more significant in the wt limb perfusions as compared to tg limbs. Immunohistology of biopsies taken after 12 hours showed less
NK
cell tissue infiltration in the tg limbs. In vitro
,
NK
cytotoxicity against
hCD
46 single tg
pEC
and wt
pEC
was similar, while lysis of double tg
HLA
‐E/
hCD
46
pEC
was significantly reduced. Finally, circulating cells of pig origin were observed during the ex vivo xenoperfusions. These cells expressed phenotypes mainly of monocytes, B and T lymphocytes,
NK
cells, as well as some activated endothelial cells.
Conclusions
Ex vivo perfusion of pig forelimbs using whole human blood represents a powerful tool to study humoral and early cell‐mediated rejection mechanisms of vascularized pig‐to‐human xenotransplantation, although there are several limitations of the model. Here, we show that (i) transgenic expression of
HLA
‐E/
hCD
46 in pig limbs provides partial protection from human
NK
cell‐mediated xeno responses and (ii) the emergence of a pig cell population during xenoperfusions with implications for the immunogenicity of xenografts.
Sprache
Englisch
Identifikatoren
ISSN: 0908-665X
eISSN: 1399-3089
DOI: 10.1111/xen.12357
Titel-ID: cdi_crossref_primary_10_1111_xen_12357
Format
–
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