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*
Bone Marrow Transplantation Section, Transplantation Biology Research Center, Surgical Service, Massachusetts General Hospital/Harvard Medical School, Boston, MA 02129; and
BioTransplant, Inc., Charlestown, MA 02129
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Induction of mixed hemopoietic chimerism leads to stable donor-specific tolerance in allogeneic and closely related xenogeneic (rat-to-mouse) combinations (8, 9, 10, 11, 12), but difficulties in achieving durable engraftment of donor hemopoietic cells limit the exploration of this approach in highly disparate discordant xenogeneic combinations. Previous studies using the pig-to-mouse bone marrow transplantation (BMT)4 model have shown that multiple host elements may resist xenogeneic porcine hemopoietic engraftment and function and that some of these factors are independent of host T, B, and NK cells (13, 14, 15, 16, 17). We have shown that murine complement is capable of resisting porcine hemopoietic engraftment through an Ab-independent mechanism (16) and that donor-specific growth factors are required for induction of durable porcine chimerism in mice (14, 17).
Our recent studies showed that lasting porcine hemopoietic chimerism and stem cell engraftment can be induced in T and B cell-deficient SCID-transgenic (SCID-Tg) mice expressing pig cytokine transgenes (17). However, the levels of porcine chimerism in the peripheral blood and spleen declined rapidly even when a high level of porcine chimerism persisted in the recipient marrow (Refs. 14 and 17 and our unpublished data). Studies in mice and rats have shown that macrophages play an important role in the rejection of porcine nonvascularized cellular xenografts (18, 19, 20). Moreover, macrophage depletion has been shown to improve engraftment of human hemopoietic cells in mice (21, 22). Thus, macrophages may play important roles in the elimination of porcine hemopoietic cells in the peripheral blood and spleen in T and B cell-deficient SCID mice.
Previous studies have shown that injection of liposome-encapsulated bisphosphonate, dichloromethylene diphosphonate (or clodronate) can deplete macrophages in vivo (23) and may facilitate the engraftment of human hemopoietic cells in mice (21, 22). It has been reported that the toxic effect of clodronate is due to the metabolism of clodronate to a nonhydrolyzable ATP analog (24). The parent compound of clodronate is the bisphosphonate, methylene diphosphonate (or medronate) (25), which has also been shown to undergo intracellular conversion to a nonhydrolyzable toxic ATP analog (24). It has recently been found that i.v. injection of medronate-encapsulated liposomes (M-liposomes) can be used to deplete macrophages in mice and nonhuman primates.5 Analysis of porcine chimerism in both murine and baboon recipients shortly after i.v. infusion of porcine BMC (24–48 h) demonstrate that M-liposome-sensitive macrophages play an important role in the early elimination of porcine cells. In the present study, we investigated the effect of macrophage depletion with M-liposomes on the induction of long term porcine hemopoietic chimerism using porcine cytokine transgenic mice that have been shown to support durable porcine hemopoiesis (17, 26). We also compared the effect of macrophage depletion on the survival of porcine hemopoietic cells in various tissues in mice that received an i.v. injection of porcine BMC, an i.p. injection of porcine PBMC, or both, to determine the primary sites of porcine cell clearance by macrophages in vivo.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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C.B-17 scid/scid (SCID) mice were obtained from the
colony maintained at the Department of Radiation Oncology,
Massachusetts General Hospital (Boston, MA). B10.D2/o mice were
purchased from The Jackson Laboratory (Bar Harbor, ME). Tg mice
carrying porcine cytokine transgenes (IL-3, GM-CSF, and stem cell
factor) were bred to SCID mice (for seven generations) to develop
immunodeficient Tg mice (SCID-Tg) (17, 26). The lack of T
and B cells in these SCID-Tg mice was confirmed by flow cytometric
(FCM) analysis as described (17). Tg mice on the B10.D2/o
background (B10.D2/o-Tg) were developed by backcrossing Tg founders to
B10.D2/o mice for six generations. All Tg mice used in this study were
screened for transgenes by tail DNA PCR using a primer for the CMV
promoter in combination with a primer for porcine IL-3, GM-CSF, or stem
cell factor, as described (17, 26). With the exception of
two experiments in which non-Tg C.B-17 SCID mice were used as
recipients of porcine PBMC alone (Figs. 4
and 6), SCID-Tg and
B10.D2/o-Tg mice were used in all studies. Mice were housed in a
specific pathogen-free microisolator environment and were used at 8–13
wk of age. MGH partially inbred, MHC-defined miniature swine kindly
provided by D. H. Sachs (27, 28) were used as bone
marrow and PBMC donors. All animals were maintained and procedures were
performed in accordance with National Institutes of Health
guidelines.
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M-liposome formation was performed as described.5 Briefly, phosphatidylcholine (Avanti Polar Lipids, Alabaster, AL) and cholesterol (Sigma, St. Louis, MO) were mixed to form a thin film. The film was dispersed in a sterile saline solution containing medronate (Sigma) to form a suspension, and the suspension was then sonicated for 2 min to produce liposomes. Blank liposomes were formed using the same lipid composition and sterile saline with the omission of medronate. M-liposomes were separated from free medronate by centrifugation before injection.
Transplantation protocol
Recipient mice were exposed to 3 Gy (for SCID-Tg and SCID mice) or 10.25 Gy (for B10.D2/o-Tg mice) of total body irradiation (TBI) from a 137Cs source (0.83 Gy/min) and transplanted within 4 to 8 h with porcine BMC, or PBMC, or BMC plus PBMC. Porcine BMC (1 x 108 per mouse) and PBMC (5 x 107 per mouse) were given i.v. and i.p., respectively (14, 17). B10.D2/o-Tg mice were also injected with 5 x 106 nonobese diabetic (NOD)/SCID-Tg BMC (17) along with porcine cells to rescue them from lethal irradiation.
FCM analysis of porcine chimerism
WBC, splenocytes, BMC, and peritoneal cavity (PerC) cells were
prepared from recipient mice, and FCM analysis was performed as
described (14, 17). Briefly, cells were stained with
PE-conjugated anti-mouse CD45 mAb (rat IgG2b; BD PharMingen, San
Diego, CA) in combination with FITC-conjugated anti-pig mAbs.
Porcine marker-positive cells not stained by anti-mouse CD45 mAb
were considered to be of swine (donor) origin. FITC-conjugated porcine
Ag-specific mAbs used in this study are 1030H-1-19 (mouse IgM
anti-pig pan tissue), 2.27.3a (murine IgG1 anti-pig MHC class I
monomorphic) (29), 74-22-15a (murine IgG2b anti-pig
myeloid/SWC3) (30), and MSA4 (murine IgG2a anti-swine
CD2) (31), 898H2-6-15 (mouse IgG2a anti-swine CD3)
(32), 74-12-4 (murine IgG2b anti-swine CD4)
(33), 76-2-11 (mouse IgG2a anti-swine CD8)
(33), and BB6-11C9 (murine IgG1 anti-swine CD21, a
generous gift from Dr. M. D. Pescovitz, Indianapolis, IN)
(34, 35). Nonspecific binding of labeled mAbs was blocked
with 2.4G2 (rat anti-mouse Fc
R mAb) (36).
Fluorescence-conjugated HOPC1 (murine IgG2a mAb) and rat IgG2a (BD
PharMingen), both with no known reactivity to mouse or pig cells,
served as negative control Abs. FCM analysis was performed on a FACScan
(BD Biosciences, Mountain View, CA), and dead cells were excluded by
gating out low forward scatter plus high propidium iodide-retaining
cells.
CFU assay
Porcine-specific colony-forming cells were assayed as previously described (14, 17). Briefly, 5 x 105 BMC from BMT recipients were resuspended in 3 ml assay medium containing 50 ng/ml porcine IL-3, and the cell suspension was then distributed into two 35-mm culture plates and incubated in 6% CO2 at 37°C for 10–14 days. Colonies were then enumerated with an inverted stage microscope (Nikon TMS, Natick, MA). It has been demonstrated in our previous studies (14, 15) that murine progenitor cells do not react with porcine IL-3.
Immunohistochemical staining
Immunohistochemistry was performed as described (17).5 Briefly, tissues (spleen and liver) were cryosectioned (5 µm), fixed with acetone, and blocked with normal serum. Liver sections were stained with Moma-1 (rat IgG2a mAb for detection of Kupffer cells), and spleen sections were stained with Moma-1 (for detection of marginal metallophilic macrophages) or F4/80 (rat IgG2b mAb that binds to red pulp macrophages) (37, 38, 39) (all of these mAbs were purchased from the Research Diagnostics, Flanders, NJ). Slides were washed and incubated with a biotinylated secondary mAb, goat anti-rat IgG (Jackson ImmunoResearch, West Grove, PA). After washing, bound secondary Abs were detected with a Vectastain ABC kit (Vector Laboratories, Burlingame, CA), and sections were then counterstained with hematoxylin.
Statistical analysis
Significant differences between group means were determined using Student’s t test (Microsoft Excel, Redmond, WA) and a p value of <0.05 was considered statistically significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Previous studies have shown that two injections (i.v.) of
M-liposomes at a dose of 160 mg/kg per injection on each of 2
consecutive days are sufficient to deplete macrophages in
mice.5 In the present study, unless indicated, recipient
mice were injected with M-liposomes (160 mg/kg in 200 µl) three times
before transplant (two injections on day -2 and one injection on day
-1 with respect to transplant), and one to three times after
transplant (one injection per day between day 1 and day 5). Mice
injected with blank liposomes or PBS were used as controls (it has been
confirmed that neither blank liposomes nor PBS has effects on porcine
cell engraftment). Immunochemical staining of tissue sections and
cytospin preparations of marrow and PerC have shown that i.v. injection
of M-liposomes depletes mainly Kupffer cells in the liver and splenic
macrophages but does not deplete phagocytic cells in bone marrow, lymph
nodes, thymus, or PerC (Cheng et al.,5 and our unpublished
data) (23). We confirmed macrophage depletion in this
study by immunohistologic analyses of spleen and liver tissues. The
pattern of macrophage depletion and their return in M-liposome-treated
mice were similar to those in mice injected (i.v.) with clodronate
liposomes in published studies (40). As shown in Fig. 1, M-liposome treatment resulted in
complete depletion of both liver Kupffer cells and splenic macrophages
(red pulp and marginal metallophilic macrophages). Kupffer cells in the
liver and red pulp macrophages in the spleen recovered rapidly in
treated mice and became indistinguishable from those of control mice
treated with PBS by 18 days. However, marginal metallophilic
macrophages in the spleen returned tardily and were not recovered by
48 days.
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We first utilized SCID-Tg mice (17), which have
normal macrophages but no T or B cells, to determine the effect of
macrophage depletion with M-liposomes on the induction of porcine
chimerism. Mice were irradiated (3 Gy) and transplanted with porcine
BMC (108/mouse i.v.) and PBMC (5 x
107/mouse, i.p.) collected from the same porcine donor.
White blood cells (WBC) were collected at various times, and chimerism
was determined by FCM analysis. As shown in Fig. 2, treatment with M-liposomes markedly
increased porcine chimerism, particularly at early time points. At wk 1
post-transplant, the percentage of porcine donor cells in the WBC of
M-liposome-treated recipients was >10-fold greater than that in PBS
controls (p < 0.01) (Fig. 2A). The effect
of M-liposomes was even more marked (90-fold increase at wk 1) when the
total number of porcine cells in the peripheral blood was compared
(Fig. 2B), as the total WBC count was markedly increased
after M-liposome treatment (see below; Fig. 7). However, porcine
chimerism in the WBC of M-liposome-treated recipients declined rapidly
and became indistinguishable from that in PBS-treated mice by 5 wk
after transplantation.
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Similar results were observed in a repeat experiment in which lethally
irradiated B10.D2/o-Tg mice were transplanted with porcine BMC and
PBMC. Macrophage depletion was also required for the induction of
chimerism in these lethally irradiated immunocompetent mice. With the
exception of one mouse, no porcine cells were detected in the WBC of
control recipients treated with blank liposomes 1 day after transplant,
whereas porcine cells were detected in the WBC of all
M-liposome-treated mice (Fig. 3). Because
three mice in the M-liposome group died on day 6 (see below, Fig.
7C), all mice were sacrificed on day 7 to determine porcine
chimerism in the recipient marrow and spleen. As shown in Fig.
3B, only one of seven control recipients showed detectable
porcine chimerism in the marrow, and splenic chimerism was not detected
in any of these mice. In contrast, porcine MHC class I+
cells were detected in the marrow and spleen of all M-liposome-treated
recipients. BMC from the M-liposome-treated recipient with the highest
porcine chimerism and from the mouse in the control group with
detectable porcine chimerism were also tested for engraftment of
porcine myeloid progenitor cells by CFU assay, and the frequencies (CFU
per 5 x 105 BMC) were 143 and 3, respectively.
Together, our results demonstrate that murine macrophages play a
powerful role in clearing highly disparate xenogeneic cells in
vivo.
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We next investigated the effect of M-liposomes on the induction of
porcine chimerism in SCID mice that were transplanted only with porcine
PBMC. Fig. 4
shows a comparison of
porcine chimerism in the WBC, spleen, marrow, and PerC of porcine
PBMC-injected (i.p.) SCID mice that were treated with M-liposomes or
with PBS. M-liposome treatment markedly increased porcine chimerism in
the WBC, spleen, and marrow, but chimerism in the PerC was comparable
between treated and control groups (Fig. 4). Since M-liposome treatment
through i.v. injection does not deplete macrophages in the PerC, the
high levels of porcine chimerism in the PerC of these mice indicate
that PerC macrophages are not efficient in eliminating porcine cells.
However, porcine cells were rapidly cleared by macrophages after they
migrated into other tissues/organs such as spleen. Because macrophages
in the bone marrow are not susceptible to depletion by i.v. injection
of M-liposomes and are inefficient in the phagocytosis of porcine
cells, the increase in marrow chimerism (Fig. 4) in M-liposome-treated
mice indicates that macrophages play an important role in preventing
the migration of porcine cells into bone marrow from PerC. Previous
studies have shown that injection of porcine BMC does not give rise to
porcine CD3+ T cells in murine recipients (14, 17). Thus, porcine T cells detected in the marrow of
M-liposome-treated recipients of porcine BMC plus PBMC at wk 8 (Fig. 2)
were porcine PBMC injected into PerC that migrated to the marrow before
macrophages have recovered. To confirm this possibility, we compared
the engraftment of porcine CD3+ cells in M-liposome-treated
SCID-Tg mice that were transplanted with porcine BMC alone or BMC plus
PBMC. As shown in Fig. 5, A
and B, porcine CD3+ T cells were detected only
in the recipients of porcine BMC plus PBMC (2.7–32%) but not in mice
receiving porcine BMC only. Similar results were observed in another
experiment. As shown in Fig. 5C, M-liposome treatment
markedly increased the concentrations of total porcine cells in the WBC
of SCID-Tg mice receiving porcine BMC only, but the majority of porcine
cells in these mice were CD3-.
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) suggests that the spleen
might be a primary site of porcine cell clearance. To determine the
role of splenic macrophages in the elimination of porcine cells in
vivo, we compared the levels of porcine chimerism between
splenectomized and sham-operated SCID mouse recipients. SCID mice were
conditioned with 3 Gy TBI and transplanted with 5 x
107 porcine PBMC (i.p.) 2 weeks after splenectomy or sham
operation. Although the average level of porcine chimerism in the WBC
appeared higher in splenectomized recipients than that in sham-operated
mice, there was no statistical significance between the two groups
(Fig. 6; p = 0.11). These
data suggest that macrophages in the spleen were not the only effector
cells involved in the clearance of porcine cells in mice. M-liposome treatment induces mortality in irradiated recipients of porcine BMT
Administration of M-liposomes i.v. led to morbidity and mortality
in irradiated recipients of porcine cells in some of our experiments.
Notably, M-liposome treatment-related death was observed only in
sublethally irradiated SCID (Fig. 7, A and B) and lethally irradiated B10.D2/o-Tg
(Fig. 7C) mice that were transplanted with porcine BMC plus
PBMC (Fig. 7, A and C), or PBMC only (Fig.
7B), but not in the recipients of porcine BMC only (Fig.
7D).
M-liposome treatment increases WBC counts in irradiated mice
Compared with PBS control mice, an early increase in the
concentration of circulating WBC was observed in M-liposome-treated
mice in all of our experiments. Fig. 8
shows the results from one of these experiments, in which SCID-Tg mice
were sublethally irradiated (3 Gy) and treated with either M-liposomes
or PBS. The numbers of murine WBC in M-liposome-treated mice became
significantly higher than those in PBS controls by 1 wk and reached
peak levels at 3 weeks. Although it remains unclear by which M-liposome
treatment elevates WBC counts, the reduction of macrophage-released
cytokines with inhibitory effects on hemopoiesis might be partially
involved. It has been shown that TNF-
, TGF-
, monocyte
chemoattractant protein-1, and macrophage-inflammatory protein-1 can
inhibit hemopoietic cell proliferation (41, 42).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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) strongly suggests that the
spleen might be a primary site of porcine cell clearance. However,
porcine chimerism was not significantly increased by depletion of
splenic macrophages only via splenectomy (Fig. 6), indicating that
M-liposome-sensitive macrophages in other tissues/organs, other than
red pulp macrophages in the spleen, also contribute to the elimination
of porcine cells in vivo. Because i.v. administration of M-liposomes
mainly depletes Kupffer cells in the liver and splenic macrophages, our
results suggest that both splenic red pulp macrophages and Kupffer
cells in the liver were involved in the clearance of porcine cells
in vivo.
Although M-liposomes markedly increased the survival of porcine cells
in the WBC, spleen, and marrow, this treatment had no effect on the
survival of porcine cells in the PerC in mice that were injected i.p.
with porcine PBMC (Fig. 4). These results implicate that macrophages in
the PerC do not phagocyte porcine cells in vivo. Macrophages in the
bone marrow also appear to be inefficient in the phagocytosis of
porcine cells, because levels of porcine chimerism in the bone marrow
remained higher in M-liposome-treated mice than in controls even after
the treatment was withdrawn. Despite the fact that depletion of
M-liposome-sensitive macrophages permitted a higher level of migration
of porcine CD3+ PBMC (injected into PerC) into the bone
marrow, the levels of porcine myeloid chimerism were not significantly
improved in the recipients of porcine BMC (i.v.) and PBMC (i.p.) by
M-liposomes (Fig. 2). This is likely because a large number of porcine
BMC were injected i.v., and only a limited number of marrow-homing
cells could enter into the host bone marrow. The number
(108) of porcine BMC injected is almost equal to the total
number of bone marrow cells in a SCID mouse (estimated by counting the
number of nucleated cells of two femora, which is equivalent to 13.5%
of the entire bone marrow compartment (44)). These results
suggest that optimal (or nearly optimal) migration of porcine
hemopoietic stem cells and progenitors could be achieved by injecting
(i.v.) a large number of porcine BMC in SCID mice without macrophage
depletion. Studies of human hemopoietic cell transplantation in SCID
mice also showed that the beneficial effect of macrophage depletion on
human cell engraftment is less apparent as increasing cell numbers
transplanted (22). However, this is not the case when
porcine hemopoietic cells are transplanted to immunocompetent mice,
which have more potent resistance to porcine cell engraftment than SCID
mice do. As shown in Fig. 3, macrophage depletion is required for the
migration of porcine cells into the host bone marrow in lethally
irradiated B10.D2/o-Tg mice.
Previously, studies have shown that IFN- may stimulate NK cells
to reject donor hemopoietic cells, and depletion of
IFN--secreting macrophages with silica or carrageenans can
facilitate mouse allogeneic and rat xenogeneic marrow engraftment in
mice (45, 46, 47, 48, 49). Consistent with these studies, it has been
reported that NK cells play an important role in the resistance of rat
marrow engraftment in mice (9, 50). However, our previous
studies using anti-asialo GM1 (which depletes NK cells) or
cyclophosphamide (which suppresses NK activity (51)) have
shown that NK cells do not play a significant role in resisting
engraftment of porcine marrow cells in SCID mice (13). In
addition, it has been recently reported that macrophages, but not NK
cells, play an important role as effector cells in the destruction of
porcine islet xenografts in mice (20). Thus, markedly
improved engraftment of porcine hemopoietic cells in M-liposome-treated
recipients is likely due to inhibited phagocytosis of porcine cells by
macrophages and not to the suppression of NK cell activity.
Phagocytosis of pathogens and senescent cells by macrophages is mediated by phagocytic receptors (52). The most important receptors involved in this process include receptors for the Fc portion of Igs (FcRs), complement receptors (CRs), and the mannose receptor. CR1 (CD35), CR3 (CD11b/CD18), and CR4 (CD11c/CD18) are most important receptors expressed by macrophages, which mediate phagocytosis of complement-opsonized particles and cells (52, 53). CR1 binds mainly C3b, C4b, and C1q (54, 55), and CR3 and CR4 are specific receptors for C3bi (52). In addition, receptors such as scavenger receptor-A, CD36, and CD14 play important roles in the phagocytosis of apoptotic cells by macrophages. The rapid elimination of porcine cells in T and B cell-deficient SCID mice demonstrates that phagocytosis of porcine cells by murine macrophages can occur independently of the FcR-mediated mechanism. Our previous studies have shown that murine complement can mediate rejection of porcine hemopoietic cells through an Ab-independent mechanism (16), suggesting that murine macrophages may recognize complement-coated porcine cells though CRs.
FcRs for IgGs (FcRs) have been demonstrated to be the most important
FcRs for triggering macrophage phagocytosis and Ab-dependent
cell-mediated cytotoxicity (52). However, the majority of
anti-pig natural Abs (NAb) in naive mice are of the IgM class
(56). Anti-pig IgG Abs are produced only after exposure to
porcine Ags, and their production is T cell dependent
(56). Although the pre-existing anti-pig IgM NAb may
mediate cytotoxicity by activation of complement, the significance of
these NAb in mediating macrophage phagocytosis of porcine cells has not
been demonstrated. It has been reported that FcµRs are expressed on
NK cells and subpopulations of T and B cells (57, 58, 59, 60, 61);
however, the functional and molecular characteristics of these
receptors are still unclear. It has been recently described that
macrophages and B cells express a receptor (FcµR) that is able to
bind IgA and IgM, and FcµR on B cells mediates endocytosis of
IgM-coated microparticles (62). Further studies are needed
to address the question of whether FcµR on macrophages could
mediate phagocytosis of porcine cells coated with anti-pig IgM
NAb.
Previous studies have demonstrated that injection (i.v.) of M-liposomes
is well tolerated in mice.5 However, M-liposome
treatment-associated morbidity and mortality were observed in
irradiated recipients of porcine cells in the present study (Fig. 7).
Because the incidence of M-liposome-associated morbidity or mortality
was markedly greater in the recipients of porcine PBMC (with or without
BMC) than those receiving porcine BMC only and because significant
engraftment of porcine CD3+ T cells was observed only in
M-liposome-treated mice that received porcine PBMC, it is possible that
the harmful effect of M-liposomes was a consequence of porcine T
cell-mediated graft-vs-host reactions. Indeed, graft-vs-host
disease-like symptoms, including hunching, diarrhea, and loss of body
weight, were observed in most mice that succumbed to M-liposome
treatment-associated lethality. In addition, infections might be also
involved, given that macrophage depletion would markedly reduce the
host defenses against bacteria and other pathogens in irradiated
recipients of porcine cells.
In summary, our results suggest that macrophage depletion at the time of stem cell transplantation might be useful as a way of improving the survival and engraftment of porcine hemopoietic cells in mice. The same approach might also be useful in primates and might thereby facilitate the induction of long term xenogeneic chimerism and tolerance. However, the rapid decline of porcine chimerism in the spleen and peripheral blood in association with macrophage returning after withdrawal of M-liposome treatment suggests that macrophages developing de novo in porcine BMT recipients were not "tolerant" of porcine cells. Therefore, continuous treatment is likely to be required for maintaining porcine chimerism. Because macrophages play a critical role in initiating immune responses against pathogens, the long term use of macrophage-depleting reagents is unlikely to be acceptable, even if nontoxic drugs could be developed. Like T, B, and NK cells, macrophages also have the ability to discriminate between self and non-self. Thus, identification of the macrophage receptors responsible for distinguishing "self" from xenogeneic cells would permit the development of strategies for making host macrophages specifically nonresponsive to porcine cells.
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Acknowledgments |
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Footnotes |
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2 Current address: Department of Surgery, Kidney Center, Tokyo Women’s Medical University, Kawada-cho 8-1, Shinjuku-ku, Tokyo, Japan.
3 Address correspondence and reprint requests to: Dr. Yong-Guang Yang, Bone Marrow Transplantation Section, Transplantation Biology Research Center, Massachusetts General Hospital, MGH East, Building 149-5102, 13th Street, Boston, MA 02129. E-mail address: yongguang.yang{at}tbrc.mgh.harvard.edu
4 Abbreviations used in this paper: BMT, bone marrow transplantation; BMC, bone marrow cells; CR, complement receptor; FCM, flow cytometry; M-liposome, medronate-encapsulated liposome; PerC, peritoneal cavity; SCF, stem cell factor; Tg, transgenic; WBC, white blood cell; TBI, total body irradiation; NAb, natural Ab.
5 J. Cheng, R. M. Glaser, D. Brigham, H. Kruger-Grey, S. Mohapatra, M. E. White-Scharf, D. K. C. Cooper, and A. D. Thall. Promotion of xenogeneic hematopoietic chimerism in rodents by mononuclear phagocyte depletion. Submitted for publication.
Received for publication July 10, 2001. Accepted for publication November 5, 2001.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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1-3Gal natural antibody-forming B cells by induction of mixed chimerism. J. Exp. Med. 187:1335.,-dichloromethylene) triphosphate, by mammalian cells in vitro. J. Bone Miner. Res. 12:1358.[Medline]
, is the endogenous chemokine that cooperates with TGF- to inhibit the cycling of primitive normal but not leukemic (CML) progenitors in long-term human marrow cultures. Blood 92:2338.. J. Immunol. 134:3739.[Abstract]
T cells and NK cells inhibit the engraftment of xenogeneic rat bone marrow cells and the induction of xenograft tolerance in mice. J. Immunol. 166:1398./µ receptor mediates endocytosis of IgM-coated microbes. Nat. Immunol. 1:441.[Medline]This article has been cited by other articles:
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  H. Wang, M. L. Madariaga, S. Wang, N. Van Rooijen, P.-A. Oldenborg, and Y.-G. Yang Lack of CD47 on nonhematopoietic cells induces split macrophage tolerance to CD47null cells PNAS, August 21, 2007; 104(34): 13744 - 13749. [Abstract] [Full Text] [PDF]
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K. Ide, H. Wang, H. Tahara, J. Liu, X. Wang, T. Asahara, M. Sykes, Y.-G. Yang, and H. Ohdan Role for CD47-SIRP{alpha} signaling in xenograft rejection by macrophages PNAS, March 20, 2007; 104(12): 5062 - 5066. [Abstract] [Full Text] [PDF]
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 J.-I. Rodriguez-Barbosa, Y. Zhao, G. Zhao, A. Ezquerra, and M. Sykes Murine CD4 T Cells Selected in a Highly Disparate Xenogeneic Porcine Thymus Graft Do Not Show Rapid Decay in the Absence of Selecting MHC in the Periphery J. Immunol., December 15, 2002; 169(12): 6697 - 6710. [Abstract] [Full Text] [PDF]
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; n = 7) or PBS
(
; n = 7) were measured 1 week after transplant.
Seven mice were initially included in each group, but three mice in the
M-liposome-treated group died between day 5 and day 6 after transplant,
and porcine chimerism in these mice was not analyzed. Data are numbers
of anti-pig pan tissue mAb 1030H1-19+ (total), myeloid,
CD3+, CD4+, CD8+, and
CD21+ porcine cells in the WBC (per milliliter blood),
spleen (SPL), bone marrow (BM; per two femurs and tibias), and PerC
(group means ± SD). *, p < 0.05; **,
p < 0.01.
) SCID mouse recipients of porcine PBMC. WBC
were prepared 1 wk after transplant, and porcine chimerism was measured
by FCM analysis using anti-pig pan tissue mAb (1030H-1-19). Each
symbol represents an individual animal. Shown are representative data
of two independent experiments.
