Background. The aim of the present study was to evaluate the nature of
T cells involved in and, presumably, critical to fetal porcine islet-
like cell cluster (ICC) xenograft rejection, Methods. Normal mice and
T cell receptor (TCR)-beta-, TCR-delta-, or TCR-beta x delta-deficient
mice were transplanted with fetal porcine ICC under the kidney capsul
e. Perforin- or granzyme B (GraB)-deficient mice were used to further
characterize T cell-dependent pathways, For evaluation of the role of
T cells in the activation process of macrophages, TCR-beta x delta mut
ants were treated with recombinant mouse tumor necrosis factor (TNF)-a
lpha. In addition, normal mice transplanted with porcine ICC were trea
ted with MDL 201,449A, a novel transcriptional inhibitor of TNF-alpha,
Results. In normal mice, the majority of the infiltrating cells were
large, macrophage-like cells expressing the macrophage specific phenot
ype marker F4/80, CD3(+) T lymphocytes were found to be mainly accumul
ated in the peripheral parts of the ICC xenograft, TCR-beta mutants an
d TCR-beta x delta mutants exhibited no signs of xenograft rejection,
whereas TCR-delta mutants and perforin- and GraB-deficient animals rej
ected the ICC xenograft. Posttransplant high-dose recombinant mouse TN
F-alpha-treatment of TCR-beta x delta mutants did not result in fetal
porcine ICC xenograft rejection. However, a somewhat increased amount
of F4/80(+) and Mac-1(+) cells was observed within the xenograft area.
Similarly, although graft survival was not found to be prolonged, red
uced numbers of CD4(+) T cells were observed in mice treated with MDL
201,449A, Conclusions, In the pig-to-mouse model, fetal porcine ICC xe
nograft rejection is exclusively dependent on T cells bearing TCR-alph
a beta chains. In addition, the absence of perforin or GraB has no inf
luence on the rejection process, suggesting that xenospecific cytolyti
c T cells are of minor importance, Even if TNF-alpha is of importance
to the developing process of ICC xenograft rejection, other cytokines,
i.e., interferon-gamma, might efficiently substitute for the lack of
TNF-alpha.