B7-1 transgene expression on the pancreatic islets in nonobese diabetic (NOD) mice leads to
accelerated diabetes, with >50% of animals developing diabetes before 12 wk of age. The expression of B7-1 directly on the pancreatic
cells, which do not normally express costimulator
molecules, converts the cells into effective antigen-presenting cells leading to an intensified autoimmune attack. The pancreatic islet infiltrate in diabetic mice consists of CD8 T cells, CD4
T cells, and B cells, similar to diabetic nontransgenic NOD mice. To elucidate the relative importance of each of the subsets of cells, the NOD-rat insulin promoter (RIP)-B7-1 animals
were crossed with NOD.
2microglobulin
/
mice which lack major histocompatibility
complex class I molecules and are deficient in peripheral CD8 T cells, NOD.CD4
/
mice
which lack T cells expressing CD4, and NOD.µMT
/
mice which lack B220-positive B
cells. These experiments showed that both CD4 and CD8 T cells were necessary for the accelerated onset of diabetes, but that B cells, which are needed for diabetes to occur in normal
NOD mice, are not required. It is possible that B lymphocytes play an important role in the
provision of costimulation in NOD mice which is unnecessary in the NOD-RIP-B7-1 transgenic mice.
Key words:
 |
Introduction |
Insulin-dependent diabetes in the nonobese diabetic (NOD)1
mouse occurs as a result of an autoimmune attack on pancreatic
cells. Although T cells play a very important role
in the process, and both CD4 and CD8 T cells are required
to adoptively transfer diabetes (1, 2), other cell types are
clearly also important in the pathogenesis of disease.
Compelling evidence for the role of CD8 T cells in the
initiation of diabetes comes from studies where the
2microglobulin (
2m)
/
mutation was bred onto the NOD
background (NOD
2mnull), generating mice in which MHC
class I expression is deficient (3, 4); consequently, these
mice have very poor development of CD8 T cells. These
NOD
2mnull mice do not develop either insulitis or diabetes (3). In addition, treatment of NOD mice with antibodies against CD8 T cells, when given before 5 wk of age,
prevents both insulitis and diabetes (7). Further support for
the role of CD8 T cells in initiation of disease has come
from studies that demonstrate that T cells from young prediabetic NOD mice can transfer diabetes to MHC class I-positive NOD.SCID mice but not NOD.SCID mice
with the
2mnull mutation lacking MHC class I (8). It is
clear that CD8 T cells also play a role in the final effector
phases of diabetes. This is shown by the fact that development of diabetes is delayed when diabetic spleen cells are
adoptively transferred into NOD
2mnull mice, but there
was no delay in disease transfer into NOD
2mnull mice
bearing
2m on the rat insulin promoter (RIP), which express MHC class I exclusively on the pancreatic
cells (9).
CD4 T cells are also clearly important in the evolution
of insulitis and for diabetes to occur, as it has also been
shown that both insulitis and diabetes are prevented using
antibodies against CD4 (10). Although adoptive transfer
experiments have shown, for the most part, that both CD4
and CD8 T cells are required for diabetes to occur (1, 2),
both CD8 T cells (11) and CD4 T cells (12) are able to
transfer disease when given alone to NOD.SCID animals,
which lack lymphocytes. T cell receptor transgenic mice
that bear a single specificity of CD4 T cells, which are reactive to pancreatic
cells, having been crossed with recombinase activating gene (RAG)-2
/
mice on the NOD
background, develop accelerated diabetes (13). In addition,
NOD mice crossed with mice that lack MHC class II molecules and are therefore deficient in CD4 T cells do not
develop insulitis (5). However, this experiment is not easily
interpreted, since these mice also have altered MHC class I
molecules. This is because the MHC class II knockout mutation is made directly into I-Ab, and therefore, when
NOD mice are crossed with I-Ab
/
mice, they will
have the MHC class I molecules Kb and Db (rather than Kd
and Db in NOD). CD4 T cells are clearly involved in the
development of disease, as adoptive transfer of diabetic
CD4 T cells alone into NOD.SCID animals will eventually
cause disease, whereas isolated CD8 T cells do not (14).
However, when cells from younger NOD donors are used,
both CD4 and CD8 T cells are required.
B cells also play a role in the development of diabetes
(15), the lack of B cells preventing development of diabetes. Although B cells are not required for adoptive transfer of diabetes (18), unable to cause disease when transferred
alone to NOD.SCID mice (our unpublished observations),
and serum does not transfer disease, B cells clearly influence
the development of diabetes in a manner that probably relates to their antigen-presenting function. However, the precise role these cells play is still to be elucidated.
We have previously described NOD mice that express
the costimulatory molecule B7-1 using the RIP on the
pancreatic
cells, which develop clearly accelerated diabetes, with >50% of mice developing diabetes before the age
of 12 wk when their nontransgenic littermates are just beginning to develop disease (19). This phenomenon is seen
as early as the first backcross generation in mice that are homozygous for H-2g7 and B7-1 transgene positive. Diabetes
in such mice occurs as early as 3 wk of age, and when examined histologically, the infiltrate is very similar to that
seen in NOD mice, with large numbers of CD4 and CD8
T cells as well as a substantial number of B220-positive B
cells (19). This study aimed at examining the role of CD4 and CD8 T cells, as well as B cells, in the accelerated model of diabetes of the NOD-RIP-B7-1 transgenic mice and
comparing them to the role of these cells in the nontransgenic NOD mouse. We postulate that the B7-1-expressing
cells are a potent stimulus for CD8 T cells that are specific for
cell peptides presented by MHC class I molecules.
When
cells are attacked by CD8 T cells, they release soluble antigens that are taken up by antigen-presenting cells
which then present peptide to CD4 T cells in a similar
manner to that found in the nontransgenic NOD mouse.
 |
Materials and Methods |
Mice.
NOD-RIP-B7-1 transgenic mice were generated by
crossing C57BL/6 mice transgenic for the human B7-1 molecule
with NOD/Caj mice from our colony (19). Mice used in the experiments were all homozygous for H-2g7, ascertained at the first
backcross, and were used at the fourth backcross generation to
NOD. NOD
2mnull mice at the ninth backcross generation were
provided by Linda Wicker (Merck, Rahway, NJ) and David Serreze (The Jackson Laboratory, Bar Harbor, ME). CD4
/
mice on H-2b background (20) were bred with NOD/Caj mice
and then backcrossed for four generations. µMT
/
mice lacking B cells (21) were obtained originally from Klaus Rajewsky
(University of Cologne, Germany) and backcrossed for nine generations onto NOD/Caj mice. The mice were all housed in specific pathogen-free conditions. NOD.SCID animals were obtained
originally from The Jackson Laboratory, and NOD.SCID-RIP-B7-1 mice were generated by crossing the NOD-RIP-B7-1 transgenic mice with NOD.SCID mice at The Jackson Laboratory
(by David Serreze) and backcrossed to NOD.SCID mice. All the
NOD.SCID-RIP-B7-1 mice used in the experiments were heterozygous for the RIP-B7-1 transgene. All the animal studies were
performed under protocols approved by the Yale University Animal Care and Use Committee.
Breeding Scheme.
The mice bearing the knockout mutations
were bred initially onto the NOD-RIP-B7-1 transgenic mice.
The F1 mice are all heterozygous for the knockout mutation and
are either transgene positive (heterozygous) or transgene negative.
F1 mice positive for the B7-1 transgene were then intercrossed
with F1 mice which were B7-1 transgene negative, in order not
to generate mice that were homozygous for the B7-1 transgene.
The frequency of mice from this cross that were homozygous for
the knockout mutation, were homozygous for H-2g7, and had the
B7-1 transgene was 2 out of 32.
Diabetes Screening.
Animals were tested weekly for glycosuria
using Diastix (Bayer Corp., Elkhart, IN), and if present, diabetes
was confirmed by a blood glucose measurement using One
Touch test strips (LifeScan, Inc., Milpitas, CA) of >250 mg/dl
(13.9 mmol/liter).
Genotyping.
The presence or absence of the hB7-1 transgene
was determined by PCR on tail DNA using the following primers,
made in the Keck Facility (Yale University): 5' TGA AGC CAT
GGG CCA CAC and 5' GAC ACT GTT ATA CAG GGC.
Typing for the various null mutations was carried out using
PCR for neomycin to identify the presence of the mutation, and then staining of peripheral blood with mAbs to identify homozygous mice as follows. Heterozygous carriers of the
2mnull allele,
CD4
/
allele, and µMT
/
allele were identified using the
following primers specific for the neomycin in the knockout mutation: 5' GGC ACA ACA GAC AAT CGG CT and 5' CCT
GAT GCA CTT CGT CCA GA. Homozygosity for the
2mnull
gene was tested for by staining peripheral blood lymphocytes with FITC-conjugated anti-CD8 (GIBCO BRL, Gaithersburg,
MD). Homozygosity for the CD4
/
mutation was tested for
by staining with FITC-conjugated anti-CD4 (GIBCO BRL).
Homozygosity for the µMT
/
mutation was tested for by
staining of peripheral blood lymphocytes with FITC-conjugated anti-mouse Ig (Sigma Chemical Co., St. Louis, MO). The mice
were screened for homozygosity for H-2g7 by testing for the absence of Kb using the mAb Y-25 and FITC-conjugated anti-
mouse IgG (Sigma Chemical Co.) followed by flow cytometric
analysis as described previously (19).
Histology.
Pancreatic tissue was fixed in formalin, paraffin
embedded, and stained with hematoxylin and eosin. The sections
were examined microscopically, and insulitis of individual islets
was assessed by two independent observers according to the scale
of 0 to 4 as follows: 0, no insulitis; 1, periinsulitis; 2, periinsulitis with some insulitis; 3, >50% of the islet infiltrated; and 4, complete islet destruction. Additionally, some of the pancreata were
fixed in periodate-lysine-paraformaldehyde, sucrose infused, and
then frozen in Tissue-Tek OCT (Bayer Corp.). Sections (7 mm thick) were stained with biotinylated YT4.3 antibody recognizing CD4, TIB 105 antibody recognizing CD8, and B220 antibody
which stains the majority of B cells. The color was developed using diaminobenzidine tetrahydrochloride and nickel ammonium sulphate. The sections were then counterstained with hematoxylin.
Adoptive Transfer Studies.
Spleens were removed from 6- and
12-wk-old female NOD mice that were nondiabetic (ascertained
by blood glucose measurement of <250 mg/dl), and recently diabetic NOD mice (ascertained by a blood glucose measurement
of >250 mg/dl).
Splenocytes (2 × 107 cells) were adoptively transferred to female NOD.SCID and NOD.SCID-RIP-B7-1 mice, and the onset of diabetes was monitored, initially by checking for glycosuria
and confirmed by measurement of blood glucose. At the onset of
diabetes, the animals were killed, and the pancreas was removed
for immunohistochemistry. In addition, 107 CD8 NOD-derived
islet-reactive cloned T cells (11) were also adoptively transferred
to these groups of mice.
 |
Results |
NOD-RIP-B7-1/
2mnull Mice Develop a Low Incidence of
Accelerated Diabetes.
NOD
2mnull mice have <1% peripheral CD8 T cells but do not develop diabetes, as reported
previously (3, 4, 6). NOD-RIP-B7-1/
2mnull also had
<1% CD8 T cells in peripheral blood, compared with 5-10% total lymphocytes in the
2m-sufficient mice (data not
shown), and 14 out of 16 mice failed to develop diabetes
(Fig. 1), even when followed until 24 wk of age. Histology
showed that these mice also did not develop insulitis (Table
1, and Fig. 2). However, surprisingly, 2 out of 16 mice that
were NOD-RIP-B7-1/
2mnull developed accelerated diabetes (Fig. 1). In the two animals that developed diabetes,
the islet infiltrate was made up of CD4 T cells and B cells
(Fig. 2), compared with NOD-RIP-B7-1 animals, which
develop diabetes in which the infiltrate consists of CD8 and
CD4 T cells as well as B cells.

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Fig. 1.
Mice were observed and screened for glycosuria. All mice
which had glycosuria had a blood glucose measurement taken using One
Touch test strips (LifeScan, Inc., Milpitas, CA), and diabetes was diagnosed if the blood glucose was >250 mg/dl. The graph shows the percentage of diabetes in mice that were RIP-B7-1 transgene positive and
2m sufficient (filled circles), n = 41; RIP-B7-1 transgene positive and 2m
deficient (open circles), n = 16; RIP-B7-1 transgene negative and 2m sufficient (filled triangles), n = 46; and RIP-B7-1 transgene negative and 2m
deficient (open triangles), n = 16. The numbers indicate the total population of both male and female mice.
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Fig. 2.
Pancreatic section from an NOD-RIP-B7-1/ 2mnull mouse that was nondiabetic is shown (top), illustrating staining with anti-CD4, anti-CD8, and anti-B220 antibodies at 24 wk, and showing that when diabetes did not occur, there was no insulitis. (Middle) Staining from one of the two
NOD-RIP-B7-1/ 2mnull mice that became diabetic, showing the presence of CD4 T cells and B cells. (Bottom) Staining of a pancreatic section from a diabetic NOD-RIP-B7-1/ 2m-sufficient mouse.
|
|
NOD-RIP-B7-1/CD4
/
Mice Do Not Develop Accelerated Diabetes.
NOD mice crossed with CD4
/
to
the fourth backcross generation do not develop either insulitis or diabetes (Fig. 3). When NOD.CD4
/
mice
were crossed with NOD-RIP-B7-1 mice, no diabetes occurred before the age of 12 wk. After 12 wk, some mice
(mainly males) did develop diabetes (Fig. 3). In contrast to
the NOD.CD4
/
mice that are RIP-B7-1 transgene
negative, where no insulitis is seen, even in the NOD-RIP-B7-1/CD4
/
mice that did not develop diabetes,
insulitis was seen, as shown in Fig. 4. The insulitis scores
are shown in Table 1. Although these mice lack the CD4 coreceptor, it has been reported previously that there is an
increased number of double-negative CD3+ T cells in
CD4
/
mice that may play the role normally taken by
CD4 T cells. In NOD-RIP-B7-1/CD4
/
mice, many
of the islet-infiltrating CD3+ cells stained with anti-CD8.

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Fig. 3.
The graph shows the percentage of diabetes in mice that
were RIP-B7-1 transgene positive and CD4 sufficient (filled circles), n = 71; RIP-B7-1 transgene positive and CD4 deficient (open circles) n = 23;
RIP-B7-1 transgene negative and CD4 sufficient (filled triangles), n = 56;
and RIP-B7-1 transgene negative and CD4 deficient (open triangles), n = 18. The numbers indicate the total population of both male and female
mice.
|
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Fig. 4.
(Top) Pancreatic sections from a non-RIP-B7-1 transgenic mouse that was CD4 deficient. All these mice were nondiabetic, and there was
no insulitis seen, as illustrated by staining with anti-CD4, anti-CD8, and anti-B220 antibodies at 24 wk. The islets are intact, as shown by staining with
insulin (red). (Middle) Staining from an NOD-RIP-B7-1/CD4 / mouse that did not become diabetic. (Bottom) Staining of a pancreatic section from a
diabetic NOD-RIP-B7-1/CD4-sufficient mouse.
|
|
NOD-RIP-B7-1/µMT
/
Mice Develop Accelerated Diabetes.
We have shown that NOD.µMT
/
mice at
the ninth and tenth backcross generation to NOD, which
are homozygous for all the NOD susceptibility markers described (15), do not develop diabetes (our unpublished observations). In contrast, when the mice are crossed with the
NOD-RIP-B7-1 mice, they develop diabetes very rapidly,
and absence of B cells in this model does not impair the development of the accelerated diabetes (Fig. 5). Histology shows that NOD.µMT
/
mice develop some insulitis
by the age of 30 wk, although they do not develop diabetes
(Fig. 6). In the NOD-RIP-B7-1 mice lacking B cells, histology at the time of diabetes shows that there is a large
number of CD4 and CD8 T cells present. There are a few
B220-positive cells that are not B cells but rather B220T
cells, such as those seen in MRL/lpr/lpr mice, as shown by
the absence of staining for Ig (Fig. 6).

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Fig. 5.
The graph shows the percentage of diabetes in mice that
were RIP-B7-1 transgene positive and B cell sufficient (filled circles), n = 35; RIP-B7-1 transgene positive and B cell deficient (open circles), n = 9;
RIP-B7-1 transgene negative and B cell sufficient (filled triangles), n = 10;
and RIP-B7-1 transgene negative and B cell deficient (open triangles), n = 13. The numbers indicate the total population of both male and female
mice.
|
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Fig. 6.
(Top) Pancreatic sections from a nontransgenic mouse that was B cell deficient taken at 30 wk. Mild insulitis is seen, as illustrated by staining
with anti-CD4, anti-CD8, and anti-B220 antibodies. (Middle) Staining from an NOD-RIP-B7-1/µMT / mouse that became diabetic, showing intense insulitis. There are a few B220-positive cells seen, but these are negative for staining with anti-Ig antibody and are likely to be T cells. (Bottom)
Staining of a pancreatic section from a diabetic NOD-RIP-B7-1, B cell-sufficient mouse.
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NOD.SCID-RIP-B7-1 Mice Develop Diabetes More Rapidly after Adoptive Transfer of Splenocytes and CD8 Cloned T
Cells Than NOD.SCID Mice.
Splenocytes from 6-wk-old
prediabetic NOD mice are able to transfer diabetes to
NOD.SCID mice in 6-10 wk. This time course is accelerated by ~3 wk, when the cells are transferred into
NOD.SCID-RIP-B7-1 mice (Fig. 7 a). A similar result is
seen when just prediabetic or diabetic spleen cells are transferred into NOD.SCID mice compared with NOD.SCID-RIP-B7-1 mice, in that diabetes is accelerated in the latter
recipients (Fig.7, b and c). When CD8 T cell clones (11),
which respond to an undefined
cell antigen, are transferred, diabetes is also accelerated in the NOD.SCID-RIP-B7-1 mice, showing that these cells can be costimulated in
vivo (Fig. 7 d). Histology indicates that there is increased
presence of CD8 T cells bearing V
6 in the infiltrate of the
diabetic NOD.SCID-RIP-B7-1 mice (Fig. 8). Staining
with anti-V
8 did not show any excess of these cells in either the diabetic NOD.SCID-RIP-B7-1 mice or the diabetic NOD.SCID mice (Fig. 8).

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Fig. 7.
Incidence of diabetes after adoptive transfer of 6-wk-old
NOD spleen cells (a), 12-wk-old NOD spleen cells (b), diabetic spleen
cells (c), and CD8 cloned T cells (d) into NOD.SCID-RIP-B7-1 mice
(filled circles) and NOD.SCID mice (open circles).
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Fig. 8.
Immunohistochemistry showing staining with anti-CD4, anti-CD8, anti-V 6, and anti-V 8 in NOD.SCID-RIP-B7-1 mice (top) and
NOD.SCID mice (bottom) that have become diabetic after adoptive transfer of spleen cells from 12-wk-old NOD mice.
|
|
 |
Discussion |
We have shown that pancreatic islets of NOD-RIP-B7-1
mice are very potent stimulators of CD8 T cells, and the
use of these islets has allowed us to clone CD8 T cells that
are able to very rapidly transfer diabetes in the absence of
CD4 T cells (11). We had noted that in the original NOD-RIP-B7-1 mice, there was no difference in the incidence
of diabetes in male and female animals, unlike the female
preponderance seen in NOD mice (19). This lack of sex
difference was also seen in the NOD-RIP-B7-1 mice that
were homozygous for the CD4
/
and µMT
/
mutations. In the NOD-RIP-B7-1 accelerated model of diabetes, we postulate that on
cells, which normally do not
express costimulatory molecules even when exposed to cytokines (reference 22, and our unpublished data), the provision of the B7-1 molecule has increased the capacity of
CD8 T cells to initiate damage to the islets, accelerating the
process that normally takes 12 wk to develop in the NOD
mouse. Indeed, under normal circumstances, as
cells do
not express costimulatory molecules, the initiation process
would be expected to occur outside the islets, perhaps in
the peripancreatic lymph nodes, with antigens shed from
the islets and presented by dendritic cells (23). As cells are
stimulated most optimally when the antigen is presented
together with the costimulatory molecules on the same cell
(24), the B7-1-expressing
cells are a potent stimulus for
CD8 T cells that are specific for
cell peptides presented
by MHC class I molecules. This may allow more T cells to
become activated or provoke local clonal expansion of
these autoaggressive T cells, or alternatively become activated earlier than in the NOD mouse. There are several
possible explanations for the fact that diabetes was seen in 2 out of 16 NOD-RIP-B7/
2mnull mice, but has not been
found in NOD
2mnull mice. It has been documented that
H-2Db is less dependent on
2m than other MHC class I
molecules, and that although reduced, the Db molecule is
expressed even in the absence of endogenous
2m (25). The presence of B7-1 on the islets could stimulate the few
CD8 T cells that have been selected on Db to initiate the
process whereby antigens are released, leading to the production of diabetes by the increased population of CD4 T
cells. In any event, the result does show that CD8 T cells
do, indeed, play an important role in the accelerated diabetes of this model, as they do in diabetes in the NOD
mouse.
It is clear from these results, and from those of other investigators, that CD4 T cells are required for the development of diabetes in the NOD mouse. The fact that accelerated diabetes does not occur in the absence of cells bearing
the CD4 coreceptor indicates that these cells are also important for the development of the accelerated diabetes
seen in the NOD-RIP-B7-1 transgenic mice. It has been
reported that CD4
/
mice have CD4
CD8
T cells that are able to perform the function of CD4 T cells (26).
In the current experiments, clearly any CD4
CD8
T
cells present do not function sufficiently to induce early diabetes in the NOD-RIP-B7-1 transgenic mice. However,
the fact that the NOD-RIP-B7-1 transgenic mice lacking
CD4 T cells can develop diabetes at a slower rate indicates
either that the CD8 T cells which have been activated can
kill the
cells alone, although less efficiently, or alternatively, that the CD4
CD8
T cells can help the process
of
cell damage, but not unless more CD8 T cells have been
activated to perform the final effector function. Certainly,
these mice had massive infiltration of CD8 T cells, which
suggests that the CD8 T cells can cause diabetes under the
conditions where they can be maximally costimulated, but
that the process is very much slower in the absence of CD4
T cells. However, the reduction of diabetes that occurs
without CD4 T cells implies that the process whereby both CD4 and CD8 T cells in the NOD mouse are required to
develop diabetes also applies to this model, and that even in
the presence of optimal stimulation of CD8 T cells, these
alone cannot cause diabetes in an accelerated fashion, although diabetes does occur after many weeks. This suggests
that soluble antigens released after damage of the islets are
taken up by professional antigen-presenting cells, such as
dendritic cells, which then perhaps present peptide to
MHC class II-restricted CD4
CD8
T cells in a similar
manner to that found in the nontransgenic NOD mouse. It
would appear that CD4 T cells are ultimately required for
the generation of accelerated diabetes, and any CD4
CD8
T cells that are present are not sufficient to perform
this function. Ultimately, the role of CD4 T cells selected
on MHC class II could be tested by crossing the NOD-RIP-B7-1 mice with class II transactivator (CIITA)
/
mice (which lack MHC class II without changing MHC
class I) (27) crossed onto the NOD background.
The presence of B cells within the islet in diabetic
NOD-RIP-B7-1 mice suggests either that B cells are
present because of bystander recruitment, or that B cells
play a role in antigen presentation to the CD4 T cells in
this accelerated model of diabetes, as in the native NOD
mouse. However, the NOD-RIP-B7-1 mice that lack B
cells are just as able to develop accelerated diabetes as those
that are B cell sufficient. This suggests that the dendritic cells and macrophages are sufficient to present antigens to
the CD4 T cells in this model, and that B cells are not required for this function. It perhaps also suggests that under
normal circumstances, the B cells are required to maximally
costimulate cells to develop diabetes. Alternatively, it is also
possible that in addition to the costimulation of autoreactive cells, the loss of costimulation of regulatory cells also
plays a role in the accelerated diabetes seen in this model.
This suggests that in addition to the role that B cells play in
antigen presentation to CD4 T cells, an important function
of B cells in diabetes in NOD mice is to provide costimulation.
It has been demonstrated previously that diabetes could
be adoptively transferred to NOD.SCID animals using
young spleen cells (28). The current study shows that there
is a delay of 3-6 wk when young spleen cells are used compared with diabetic spleen cells. There appears to be a proportional delay in the onset of diabetes, presumably related
to the presence of cells that have already been primed to
damage the
cells, taken from the older NOD animals. It
is of interest that there is a predominant population of CD8
T cells expressing V
6 in the islets of adoptively transferred NOD.SCID-RIP-B7-1 mice. CD8 T cells expressing V
6
are also found in the diabetic nontransgenic NOD.SCID
animals. In this study, T cells expressing V
8, postulated to
be important in early initiating events (29), were not seen.
We have previously isolated very potent CD8 T cell clones
that also express V
6 from the islets of young, prediabetic
NOD mice (11), which are maintained in culture on nontransgenic NOD islets. These are able to cause rapid diabetes in irradiated NOD mice and NOD.SCID mice. This
suggests that these cells are present in the islets of NOD
mice, but in the presence of the B7-1 transgene, this particularly pathogenic population is increased and is therefore
able to accelerate the onset of diabetes in the NOD.SCID
mice bearing the RIP-B7-1 transgene.
In conclusion, the results presented here suggest that in
the NOD-RIP-B7-1 mice, CD8 T cells are required for
the accelerated diabetes seen, and in addition, CD4 T cells
are also required, although diabetes can occur later in the
absence of T cells bearing the CD4 coreceptor. Whether
this result would be obtained in the absence of cells selected on MHC class II remains to be tested. However, unlike the nontransgenic NOD mouse, where B cells are required for the development of disease, these cells are not
required in the RIP-B7-1 transgenic µMT
/
mouse.
The mechanism by which the accelerated diabetes occurs is
likely to be the increase in a potent population of CD8 T
cells, which are able to initiate damage and destroy the islets, but this clearly requires the presence of CD4 T cells
for the maximum effect to be seen. Although costimulatory molecules have not been shown to be expressed on the
pancreatic islets under normal circumstances, this model
has many features similar to that seen in NOD mice, and
may allow us to elucidate the nature of the interaction between CD4 and CD8 T cells in the production of diabetes.
In addition, as both CD4 and CD8 T cells appear to be required for this accelerated diabetes, the model will also be
useful for testing preventative strategies.
Address correspondence to F. Susan Wong, Section of Immunobiology, Yale University School of Medicine, New Haven, CT 06510. Phone: 203-785-5386; Fax: 203-737-1765; E-mail: susan.wong{at}yale.edu
This work was supported by a Juvenile Diabetes Foundation International (JDFI) Career Development
Award to F.S. Wong, a JDFI Research Grant to F.S. Wong, and National Institutes of Health grants DK-51635 and DK-43078 to C.A. Janeway, Jr. R.A. Flavell and C.A. Janeway, Jr., are investigators of the
Howard Hughes Medical Institute.
1.
|
Miller, B.J.,
M.C. Appel,
J.J. O'Neil, and
L.S. Wicker.
1988.
Both the Lyt-2+ and L3T4+ T cell subsets are required for
the transfer of diabetes in nonobese diabetic mice.
J. Immunol.
140:
52-58
[Abstract/Free Full Text].
|
2.
|
Bendelac, A.,
C. Carnaud,
C. Boitard, and
J.-F. Bach.
1987.
Syngeneic transfer of autoimmune diabetes from diabetic
NOD mice to healthy neonates: requirement for both L3T4+
and Lyt2+ T cells.
J. Exp. Med.
166:
823-832
[Abstract].
|
3.
|
Serreze, D.V.,
E.H. Leiter,
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