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IMMUNOBIOLOGY
Long-Term Fetal Microchimerism in Peripheral Blood Mononuclear Cell Subsets
in Healthy Women and Women With Scleroderma
By Paul C. Evans, Nathalie Lambert, Sean Maloney, Dan E. Furst, James M. Moore, and J. Lee Nelson
Fetal CD34ⴙ CD38ⴙ cells have recently been found to persist
in maternal peripheral blood for many years after pregnancy.
CD34ⴙ CD38ⴙ cells are progenitor cells that can differentiate
into mature immune-competent cells. We asked whether
long-term fetal microchimerism occurs in T lymphocyte, B
lymphocyte, monocyte, and natural-killer cell populations of
previously pregnant women. We targeted women with sons
and used polymerase chain reaction for a Y-chromosome–
specific sequence to test DNA extracted from peripheral
blood mononuclear cells (PBMC) and from CD3, CD19, CD14,
and CD56/16 sorted subsets. We also asked whether persistent microchimerism might contribute to subsequent autoimmune disease in the mother and included women with the
autoimmune disease scleroderma. Scleroderma has a peak
incidence in women after childbearing years and has clinical
similarities to chronic graft-versus-host disease that occurs
after allogeneic hematopoietic stem-cell transplantation,
known to involve chimerism. Sixty-eight parous women
were studied for male DNA in PBMC and 20 for PBMC
subsets. Microchimerism was found in PBMC from 33% (16
of 48) of healthy women and 60% (12 of 20) women with
scleroderma, P ⴝ .046. Microchimerism was found in some
women in CD3, CD19, CD14, and CD56/16 subsets including
up to 38 years after pregnancy. Microchimerism in PBMC
subsets was not appreciably more frequent in scleroderma
patients than in healthy controls. Overall, microchimerism
was found in CD3, CD19, and CD14 subsets in approximately
one third of women and in CD56/16 in one half of women.
HLA typing of mothers and sons indicated that HLA compatibility was not a requirement for persistent microchimerism
in PBMC subsets. Fetal microchimerism in the face of HLA
disparity implies that specific maternal immunoregulatory
pathways exist that permit persistence but prevent effector
function of these cells in normal women. Although microchimerism in PBMC was more frequent in women with scleroderma than healthy controls additional studies will be necessary to determine whether microchimerism plays a role in
the pathogenesis of this or other autoimmune diseases.
r 1999 by The American Society of Hematology.
B
Twenty women with SSc with sons were studied with the mean age
of 48.8 years (34 to 71). The mean number of children was 3.8 (1 to 7)
with mean number of sons 1.8 (1 to 4). The mean age at birth of the first
child was 24.1 years (17 to 36), mean age at birth of first son was 24.8
years (18 to 36), mean age at birth of last child was 28 years (23 to 36),
and mean age at birth of last son was 27.3 years (20 to 36). The mean
age of the last child to be born was 19.6 years (1 to 40) and the mean age
of the last son to be born was 21.1 years (1 to 42). The mean age at
diagnosis of SSc was 44.1 years (29 to 62) and the mean time between
birth of first child and diagnosis of SSc was 17.3 years (2 to 42).
Specimens were also collected from 2 nulligravid women and 22 parous
women who had not given birth to a son.
DNA extraction from peripheral blood mononuclear cells (PBMC).
A total of 30 mL acid-citrate-dextrose (ACD)–preserved peripheral
blood was purified by ficoll hypaque density centrifugation. DNA was
extracted from PBMC using the Isoquick Nucleic Acid Extraction Kit
(Orca Research Inc, Bothell, WA) in accordance with the manufacturer’s instructions.
DNA extraction from fluorescent-activated cell sorted (FACS) PBMC
subsets. PBMC were purified from ACD–preserved blood as described above and resuspended in phosphate-buffered saline (PBS)/1%
fetal calf serum (FCS). Ten to 20 ⫻ 106 cells were aliquotted into three
tubes and stained with anti-CD3 fluorescein isothiocyanate (FITC) and
IDIRECTIONAL TRAFFIC of cells at the fetal-maternal
interface has been shown during pregnancy.1 Moreover,
fetal progenitor cells have been found to persist in maternal
peripheral blood for decades after childbirth.2 Progenitor cells
can differentiate into mature immune-competent cells. We
therefore asked whether persistent fetal microchimerism also
occurs in peripheral blood mononuclear cell (PBMC) subpopulations including T and B lymphocytes, monocytes, and naturalkiller (NK) cells. As discussed by Lo et al,1 maternal-fetal cell
trafficking has important biological ramifications in the context
of hematopoietic stem cell transplantation, vertical transmission
of infectious agents, and maternal tolerance of the fetus during
pregnancy. Persistent fetal microchimerism also has potential
implications for some autoimmune diseases. Scleroderma (systemic sclerosis; SSc) is an autoimmune disease with a strong
predilection for women, a peak incidence in women after
childbearing years,3 and clinical similarities to chronic graftversus-host disease (cGVHD).4 We therefore also studied
women with this disease. In this paper we report evidence for
fetal microchimerism in PBMC and PBMC subpopulations of
previously pregnant healthy women and women with scleroderma. Women with sons were recruited and Y chromosome
DNA and fetal-specific HLA DNA were used as markers of
persistent fetal-cell microchimerism.
MATERIALS AND METHODS
Subjects. Clinical specimens were collected from 48 healthy women
with sons including 13 sisters of women with SSc. The mean age was
43.1 years (34 to 71). The mean number of children was 2.2 (1 to 7) with
mean number of sons 1.7 (1 to 6). The mean age at birth of the first child
was 27.5 years (15 to 39), mean age at birth of first son was 28.1 years
(15 to 39), mean age at birth of last child was 30.3 years (15 to 39), and
mean age at birth of last son was 29.5 (15 to 39). The mean age of the
last child to be born was 12.8 years (0 to 45) and mean age of the last
son to be born was 15.1 (0 to 45).
Blood, Vol 93, No 6 (March 15), 1999: pp 2033-2037
From the Fred Hutchinson Cancer Research Center, Seattle, WA.
Submitted August 24, 1998; accepted November 11, 1998.
Supported by NIH grants AI38583 and AI41721 and the Scleroderma
Federation.
Address correspondence to J. Lee Nelson, Immunogenetics D2-100,
Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N,
Seattle, WA 98109.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be hereby marked ‘‘advertisement’’ in accordance with 18 U.S.C. section 1734 solely to indicate
this fact.
r 1999 by The American Society of Hematology.
0006-4971/99/9306-0020$3.00/0
2033
From www.bloodjournal.org by guest on January 15, 2017. For personal use only.
2034
anti-CD56/16 PE (tube 1), anti-CD14 FITC and anti-CD19 PE (tube 2),
and anti-CD34 PE and anti-CD14 FITC (tube 3). Four µL of each
fluorescently conjugated antibody (Becton Dickinson, Mountain View,
CA) was used for staining a total volume of 500 µL. Tubes were
incubated on ice in the dark for 30 minutes then washed twice with 5 mL
PBS/1% FCS before FACS sorting. Cells were sorted into CD3⫹,
CD56/16⫹, CD14⫹, and CD19⫹ populations. A proportion of sorted
cells was then examined by FACS to check purity, which was always
95% to 99%. Cells were then collected by centrifugation and stored
above liquid nitrogen. DNA was extracted using the Isoquick Nucleic
Acid Extraction Kit (Orca Research Inc) and Y-chromosome–specific
PCR was performed. DNA was routinely extracted from 0.5 ⫻ 105 cells
although occasionally smaller or greater numbers were studied.
Detection of fetal microchimerism by PCR for Y-chromosome–
specific DNA. Nested PCR for a single-copy Y-chromosome–specific
sequence was modified from Lo et al5; reagents were supplied by Perkin
Elmer unless otherwise stated. Measures were taken to prevent contamination including dedicated rooms, equipment, and reagents for PCR
reaction mix and product analysis and use of three laminar flow hoods
for DNA extraction, reaction mix preparation, and transfer of primary
products after step 1. For step 1 each reaction tube contained 1 µg
template DNA, 50 pmol sense primer (5-CTAGACCGCAGAGGCGCCAT-3; Oligos Etc) and 50 pmol antisense primer (5-TAGTACCCACGCCTGCTCCGG-3; Oligos Etc), 200 µM dNTPs, 1.5mmol/L MgCl2,
1 ⫻ Taq polymerase buffer, 1 µL Perfect Match Enhancer (Stratagene,
La Jolla, CA), and 1µL Amplitaq gold. Forty cycles were performed
(94°C for 1 minute, 67°C for 1 minute, 72°C for 2 minutes). For step 2
each reaction tube contained 2 µL reaction product from step 1 DNA, 50
pmol sense primer (5-CATCCAGAGCGTCCCTGGCTT-3; Oligos Etc)
and 50 pmol antisense primer (5-CTTTCCACAGCCACATTTGTC-3;
Oligos Etc), 200µmol/L dNTPs, 1.5 mmol/L MgCl2, 1 ⫻ Taq polymerase buffer, 1 µL Perfect Match Enhancer (Stratagene) and 1µL Amplitaq
gold. Twenty five cycles were performed (94°C for 1 minute, 55°C for 1
minute, 72°C for 2 minutes). Positive (male DNA) and negative (water)
controls were included in each run. A total of 5 µL PCR product was
electrophoresed in a 2% agarose gel (Sigma Chemical Co, St Louis,
MO) using TAE buffer (0.04 mol/L Tris-acetate, 0.001 mol/L EDTA).
Gels were photographed over ultraviolet light after staining with
ethidium bromide. Serial dilutions showed that the DNA equivalent of
one male cell could be detected in a background of 4 ⫻ 105 female cells.
No amplification was observed from negative water controls or from
DNA extracted from nulligravid women. Southern blotting was performed onto nylon membrane (Boehringer Mannheim, Mannheim,
Germany) following the manufacturer’s instructions to confirm specificity. A PCR product-specific oligonucleotide (58-CAGCTCGGCTTCGATGTGACTCTT-38) was end labelled with ␥-ATP (Amersham, Arlington
Heights, IL) and used to hybridize against blotted PCR product to
confirm specificity.
Detection of fetal microchimerism by PCR for HLA-specific sequences. The presence of fetal microchimerism was substantiated
further in some patients using HLA-specific PCR. PCR reactions were
performed in a volume of 50 µL containing 1.5 µg genomic DNA, 10
mmol/L Tris-HCl (pH 8.3), 50 mmol/L KCl, 1.5 mmol/L MgCl2,
0.001% wt/vol gelatin, 260 µmol/L of each deoxynucleotide, 0.5 U
Perfect Match Enhancer (Stratagene), 2.5 U Amplitaq Gold DNA
Polymerase (Perkin Elmer-Cetus, Norwalk, CT) and 20 pmol of each of
the HLA-specific primers. Amplification consisted of 5 minutes at 96°C
followed by 35 cycles at 95°C for 35 seconds, 55 to 65°C for 35 seconds
and 72°C for 1 minute with a final extension step at 72°C for 10 minutes
using a Gene Amp System 9600 (Perkin Elmer-Cetus). Optimum
amplification sensitivity and specificity was achieved for each primer
set by titrating MgCl2 and primer concentrations and optimizing
annealing temperature and number of thermocycles. To control for
nonspecific amplification of background HLA alleles, DNA was
extracted from control PBMC or from Epstein-Barr virus (EBV)–
EVANS ET AL
transformed human B-lymphoblastoid cell lines expressing HLA alleles
of the mother (and not the child). Negative controls comprising all PCR
reagents without DNA were also included. DNA from the subject’s
child served as a positive control for HLA-specific PCR.
Statistical analysis. Calculations of statistical significance were
done using the Mantel-Haenszel test of the null hypothesis that the odds
ratio is equal to one (StatXact program).
RESULTS
Fetal microchimerism in PBMC of healthy women and
women with scleroderma with sons. Thirty-one percent (11 of
35) of normal healthy women had Y chromosome DNA in
PBMC. Patients with SSc were more frequently positive for Y
chromosome DNA in PBMC than healthy women; 60% of SSc
patients were positive, P ⫽ .042 (Table 1). The frequency of Y
chromosome PCR-positive PBMC was not significantly different amongst sisters of women with SSc and healthy women.
Patients with SSc were more frequently positive for Y chromosome DNA in PBMC than the combined control population of
healthy women and sisters of women with SSc; 60% of SSc
patients were positive compared with 33% controls, P ⫽ .046.
In control experiments we found that two nulligravid women
were consistently negative for Y-chromosome–specific DNA.
However, 10 of 22 parous women who had never given birth to
a male were positive (5 patients and 5 controls). Eight of the 10
had prior pregnancy loss and/or transfusions that represent a
potential source of Y chromosome DNA in these subjects.
The presence of DNA from a son as detected by
Y-chromosome–specific DNA PCR was confirmed in some
families by use of HLA-specific PCR. In these families HLA
differences of the son were exploited to study DNA extracted
from PBMC of the patient. In one family DRB1*01-specific
primers were used, in two families DRB5-specific primers, and
in another family B44 (HLA class I)-specific primers were used.
Fetal microchimerism in PBMC subsets of healthy women
and women with scleroderma. PCR for Y chromosome DNA
was performed on FACS sorted subsets for 20 women. Eleven
controls comprised 9 normal healthy women and 2 healthy
sisters of women with SSc. All subjects were positive for Y
chromosome DNA in unsorted PBMC. Table 2 shows that
Y-chromosome–positive cells were frequently detected in PBMC
subsets for both controls and patients. Three of 10 (30%)
controls and 3 of 9 (33%) scleroderma patients were positive in
CD3⫹ cells. In CD56/CD16⫹ cells 4 of 9 (44%) and 5 of 8
Table 1. Male DNA in DNA Extracted From Peripheral Blood
Mononuclear cells of Women With at Least one son
Normal women
SSc sisters
SSc patients
Controls combined (normals plus
SSc sisters)
Y-PCR
Positive (%)
P Value v SSc
Patients
31 (11/35)
38 (5/13)
60 (12/20)
P ⫽ .042
P ⫽ .23
—
33 (16/48)
P ⫽ .046
Results of testing DNA extracted from PBMC for a Y chromosome–
specific sequence are summarized for 68 women; 35 normal healthy
women, 13 healthy sisters of SSc patients (one patient contributed
two sisters), and 20 women with SSc. All subjects had previously
given birth to a male child. Many women had also given birth to
daughters and some women had history of prior pregnancy loss.
From www.bloodjournal.org by guest on January 15, 2017. For personal use only.
MICROCHIMERISM IN PBMC
2035
Table 2. Persistent Microchimerism in Peripheral Blood
Mononuclear cell Subsets in Healthy Women and Women
With Scleroderma
NL2
NL4
NL44
NL45
NL47
NL52
NL56
NL61
NL67
Sister SSc8
Sister SSc27
SSc8
SSc11
SSc20
SSc26
SSc27
SSc29
SSc32
SSc4
SSc33
CD3
CD56/16
CD14
CD19
⫺
⫺
⫹‡
nd
⫺‡
⫹
⫺
⫺
⫹
⫺‡
⫺
⫹
⫺
⫺
⫹†
⫺
⫺†
⫹
⫺
⫺
⫹
⫹†
⫺
nd
⫹†
⫺
⫺*
⫺
⫹
nd
⫺†
nd
⫹†
⫺
⫺*
⫹*
⫹†
⫹
⫹
⫺
⫺
⫹*
⫹
⫺
⫺
⫺
⫺*
⫺
⫹
⫺†
⫹†
⫺
⫺
⫹†
⫺
⫹
⫺†
⫺
⫺
⫺
⫹†
⫹*
⫺*
⫹
⫺
⫺
⫹†
⫺
⫹
⫺†
⫺†
⫺
⫺
⫺
⫹†
⫺*
nd
⫺
⫺
⫹
DNA extracted from 0.5 ⫻ 105 sorted cells was tested unless
otherwise noted. The distribution of Y chromosome PCR-positive and
-negative PBMC subsets for 18 women who previously gave birth to at
least one son. Two patients (SSc33 and SSc4) had not given birth to a
son, but had a history of prior pregnancy loss and/or blood transfusion. All women were positive for Y chromosome–specific DNA upon
analysis of PBMC.
Abbreviation: nd ⫽ not done.
*0.2 to less than 0.5 ⫻ 105 cells were tested.
†Greater than 0.5 ⫻ 105 to less than 0.9 ⫻ 105 were tested.
‡Between 0.9 ⫻ 105 and 1.8 ⫻ 105 cells were tested.
(63%) were positive. In CD14⫹ cells 4 of 11 (36%) and 2 of 9
(22%) were positive. In CD19⫹ cells 5 of 11 (45%) and 2 of 8
(25%) were positive respectively. Two patients had not given
birth to a male child, however, patient SSc4 had two prior
pregnancy losses and received transfusions at the time of
childbirth and patient SSc33 had prior pregnancy loss.
HLA compatibility and microchimerism in PBMC subsets.
Family HLA studies were completed for 17 women (sons of 1
woman were not available and 2 did not have a son as noted
above). Sons were HLA class-II incompatible with their mothers for DRB1, DQA1, and DQB1 in the majority of families
(53%). Nevertheless, persistent microchimerism was found in
PBMC subsets in all of these women (Table 3). Persistent
microchimerism was detected in each of the subsets, CD3,
CD56/16, CD14, and CD19 in some women. No significant
difference was apparent for 8 women with a son who was
compatible for 1 or more of the class-II loci, DRB1, DQA1,
and/or DQB1. Again, persistent microchimerism was detected
in some women in each of the subsets, CD3, CD56/16, CD14,
and CD19.
DISCUSSION
Application of molecular biological techniques to the study
of human pregnancy has resulted in the appreciation that there is
bidirectional traffic of cells between mother and child.1 Moreover, fetal progenitor cells have been found to persist in the
maternal peripheral blood for decades after pregnancy.2 Because progenitor cells can differentiate into other immunecompetent cells populations, we asked whether persistent
microchimerism occurs in PBMC subpopulations. Y chromosome DNA served as a marker for persistent male fetal cells in
women who had previously given birth to a son. Healthy
women frequently had male DNA in their PBMC despite a
mean age of the last son to be born of 15 years.
Long-term persistence of fetal cells has potential biological
significance,1 including the possibility that these cells could be
involved in some autoimmune diseases.6 We studied women
Table 3. HLA-Compatibility of a Previously Born son and Persistent Microchimerism in Peripheral Blood Mononuclear cell Subsets
ID
Age of Sons
CD3
CD56/16
CD14
CD19
NL2
NL4
NL44
NL45
NL47
NL52
NL56
NL61
NL67
Sister 8
Sister 27
SSc8
SSc11
SSc20
SSc26
SSc27
SSc29
22, 11, 10, 6
7, 6
20
33, 29
10
1
32, 26
15, 12
2, ⬍1*
18
4
21
22, 18
33, 29
44, 33
12, 10
38
⫺
⫺
⫹
nd
⫺
⫹
⫺
⫺
⫹
⫺
⫺
⫹
⫺
⫺
⫹
⫺
⫺
⫹
⫹
⫺
nd
⫹
⫺
⫺
⫺
⫹
nd
⫺
nd
⫹
⫺
⫺
⫹
⫹
⫺
⫹
⫹
⫺
⫺
⫺
⫺
⫺
⫹
⫺
⫹
⫺
⫺
⫹
⫺
⫹
⫺
⫹
⫹
⫺
⫹
⫺
⫺
⫹
⫺
⫹
⫺
⫺
⫺
⫺
⫺
⫹
⫺
nd
HLA-compatible Son? Yes: ⫹ No: ⫺
A⫹ B⫹ C⫹
A⫺ B⫺ C⫺
nd
A⫹ B⫺ C⫹
A⫹ B⫺ C⫹
nd
A⫺ B⫹ C⫺
nd
nd
nd
A⫹ B⫹ C⫹
A⫺ B⫺ C⫺
A⫹ B⫺ C⫹
A⫹ B⫺ C⫺
A⫺ B⫺ C⫺
A⫺ B⫺ C⫺
nd
DRB1⫹
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫹
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫺
DRB1⫹
DRB1⫹
DRB1⫺
DRB1⫺
DRB1⫺
DQA1⫹
DQA1⫺
DQA1⫺
DQA1⫺
DQA1⫺
DQA1⫹
DQA1⫹
DQA1⫹
DQA1⫺
DQA1⫹
DQA1⫺
DQA1⫺
DQA1⫹
DQA1⫹
DQA1⫺
DQA1⫺
DQA1⫺
DQB1⫹
DQB1⫺
DQB1⫺
DQB1⫺
DQB1⫺
DQB1⫹
DQB1⫹
DQB1⫹
DQB1⫹
DQB1⫺
DQB1⫺
DQB1⫺
DQB1⫹
DQB1⫹
DQB1⫺
DQB1⫺
DQB1⫺
Abbreviation: nd ⫽ not done.
*Tested 4 months after delivery.
SSc4, SSc33, and SSc32 not shown; the former two had first trimester pregnancy losses and sons of the latter were not available for testing.
From www.bloodjournal.org by guest on January 15, 2017. For personal use only.
2036
with SSc because of the hypothesized link between microchimerism and development of this autoimmune disease.6 SSc is a
progressive and often fatal connective tissue disease characterized by inflammation, fibrosis, and obliterative vasculopathy of
skin, lung, heart, kidney, and gut.7 SSc shares a number of
characteristics with cGVHD that may arise after hematopoietic
stem-cell transplantation,4 has a higher incidence among women
than men, and rises sharply following childbearing years.3 A
significantly greater proportion of women with SSc had male
DNA in PBMC compared with control women with sons. The
mean age since last birth of a son in SSc patients was 21 years.
The nested PCR test employed was not quantitative, but the
difference between healthy women and women with SSc could
reflect a quantitative difference because negative subjects may
harbor fetal cells at a level below the sensitivity of the test. This
is consistent with our previous report of a smaller series
that was limited to testing of whole blood samples in which
it was shown that women with SSc compared with controls
harbor a greater quantity of DNA of fetal origin in peripheral
blood.8
In PBMC subpopulations we found persistent microchimerism in the majority of healthy women and also in women with
scleroderma. Ninety percent of women had microchimerism in
some PBMC subpopulation, either in T lymphoctyes, B lymphoctyes, monocytes, and/or in NK cell populations. Only one
woman was positive for all subpopulations, and this subject had
the most recent delivery of a son. Thus, most women evidenced
persistent microchimerism in some, but not all PBMC subpopulations. Microchimerism may be detected more readily after
application of FACS because greater concentrations of specific
PBMC subsets can be tested than would be present in whole
PBMC. Due to the relative purity with which PBMC subpopulations can be attained with FACS it is possible that microchimerism detected could be from a contaminating-cell subset. The
nested PCR was sensitive, capable of detecting the DNA
equivalent of a single cell so that if, for example, sorting purity
was 95% there could be a 1 in 20 chance that microchimerism
detected was not from the subset of interest. Whereas it is
possible that an individual determination could be in error, a
systemic error is unlikely, purity was always greater than 95%,
and most subjects were studied on more than one occasion and
with multiple aliquots of cells. It is therefore unlikely that this
consideration impacts the overall study results.
Long-term microchimerism of fetal cells in the peripheral
blood of parous women is a recent concept.2 Persistence of fetal
cells after nonterm pregnancies has not been specifically
studied, but is the most likely explanation for positive results in
some women without a son. Fetal cells have been detected in
maternal peripheral blood as early as 5-weeks gestation.9 In
control experiments we found Y chromosome positivity in 10
parous women without sons, all but two of whom had history of
prior pregnancy losses and/or had received blood transfusions.
Another potential source is through transfusion that has, in
some cases, led to the development of GVHD.10,11 A potential
source of male chimeric cells remains unexplained for two
women who may have experienced an unrecognized early
pregnancy loss. Although the possibility of contamination
cannot be entirely ruled out, stringent measures were employed
EVANS ET AL
to minimize this risk and negative controls were consistently
negative. A final potential source of microchimerism is engraftment of cells from a twin that could occur early in pregnancy
with later unrecognized loss of the twin. Chimeric cells were
first described by Owen12 who detected red blood cell antigen
sharing between dizygotic twin cattle. Interestingly, one control
woman in the present study, with two daughters and one early
pregnancy loss also had a twin brother, and was consistently
positive for Y chromosome DNA.
The factors facilitating microchimerism are poorly understood. It can be envisaged that patient age and/or time since
childbirth could influence fetal-cell microchimerism; however,
there was no readily apparent correlation of these variables with
results in our study. Total parity also did not correlate with
microchimerism.
Persistent fetal microchimerism raises the issue of maternal
tolerance to fetal paternally inherited HLA antigens. Maternal
T-cell13 and humoral14 awareness of paternally inherited antigens has been shown during and after pregnancy. In a murine
model it was found that fetal cells are cleared from the maternal
circulation more rapidly after allogeneic matings than syngeneic.15 In this study there was no apparent correlation between
HLA compatibility of a son and the long-term persistence of
male DNA in PBMC subsets. We found evidence for persistent
microchimerism in CD3⫹, CD56/CD16⫹, CD14⫹, and CD19⫹
PBMC subsets in healthy women and in women with SSc for
whom all previously born sons were HLA-incompatible.
In summary, our findings show that persistent fetal microchimerism is not uncommon in normal healthy women in
T-lymphocyte, B-lymphocyte, NK, and monocyte-cell populations. Significantly, more women with SSc had microchimerism
in unsorted PBMC than controls, however, additional studies
will be necessary to address the potential role of microchimerism in the pathogenesis of SSc and other autoimmune
diseases.
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2. Bianchi DW, Zickwolf GK, Weil GJ, Sylvester S, De Maria A:
Male fetal progenitor cells persist in maternal blood for as long as 27
years postpartum. Proc Natl Acad Sci USA 93:705, 1996
3. Silman AJ, Hochberg MC: Scleroderma, in Silman AJ, Hochberg
MC (eds): Epidemiology of the Rheumatic Diseases. Oxford, UK,
Oxford, 1993, p 192
4. Furst DE, Clements PJ, Graze P, Gale R, Roberts N: A syndrome
resembling progressive systemic sclerosis after bone marrow transplantation. A model for scleroderma? Arthritis Rheum 22:904, 1979
5. Lo YMD, Patel P, Sampietro M, Gillmer MDG, Fleming KA,
Wainscoat JS: Detection of single-copy fetal DNA-sequence from
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1999 93: 2033-2037
Long-Term Fetal Microchimerism in Peripheral Blood Mononuclear Cell
Subsets in Healthy Women and Women With Scleroderma
Paul C. Evans, Nathalie Lambert, Sean Maloney, Dan E. Furst, James M. Moore and J. Lee Nelson
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