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My
research focuses on identifying mechanisms of inducing
and abrogating immunological tolerance. Our long-term goal
is to translate our findings into novel therapies for preventing
graft rejection.
We have previously determined that
tolerance by oral or ocular administration of proteins
induces CD8+ suppressor T (Ts) cells that can transfer
unresponsiveness to naïve,
syngeneic mice. Recently, we have developed the methodology
to induce antigen-specific by stimulating CD8+ T suppressive
cells from TCR transgenic (Tg) mice in the presence of TGFbeta.
These T cells express FoxP3 inhibit the in vitro activation
of CTL responses by normal B6 CD8+ T cells specific for s
defined alloantigen but only if the alloantigen and the antigen
recognized by the CD8+ T cells are presented by the same
antigen presenting cells. The TGFbeta-activated TCR T Tg
cells also suppressed the rejection of heterotopic vascularized
cardiac allografts in normal mice mediated by specific CD4+
TCR Tg T cells, if the cardiac allograft expressed both antigens
as transgenes. Prolonged survival of allografts was associated
with rapid migration of the FoxP3+ CD8+ Ts cells into the
donor hearts. We are in the process of extending these
results to ocular transplant models as described below.
We are also studying the transplantation of retinal pigment
epithelial (RPE) cells as a treatment for age-related macular
degeneration (AMD), which is the leading cause of blindness
in people over the age of 65 in this country. This disease
ultimately results from the loss of light sensing (photoreceptor)
cells; however, the loss of photoreceptor cells is preceded
by loss of the underlying RPE. Replacement of dead or damaged
cells with healthy retinal cells is a very promising approach
to the treatment of this, and other, retinal diseases that
we are investigating. In addition, we have initiated studies on preventing
corneal graft rejection in high risk eyes.
Although the eye is an immunologically privileged site, our preliminary data
show that allogeneic RPE transplanted into the subretinal space of allogeneic
mice are rejected within 4 weeks, whereas they are not rejected in syngeneic
mice or immunodeficient Rag-1 knockout allogeneic mice. Our goal is to develop
methods to prevent rejection by inducing tolerance. To this end, we have produced
transgenic mice expressing OVA in the retinal cells, which will be transplanted
into syngeneic mice that have been adoptively transferred with OVA-specific TCR
transgenic T cells to track specific cellular interactions in vivo. Experiments
are currently underway to determine whether RPE expressing OVA are rejected by
OVA-specific T cells and whether rejection can be abrogated by induction of tolerance
to OVA or by transfer of CD8+ TCR Tg T cells activated in the presence of TGFbeta.
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