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A quantitative study of the pregnancy zone protein in the sera of pregnant and puerperal women
A quantitative
study of the pregnancy zone
protein in the sera of pregnant and puerperal women BO
VON
Umea”,
SCHOULTZ
Sweden
The serum concentration of the pregnancy zone protein (PZ) was measured by means of single radial immunodiffusion in 72 primigravidas who were followed during pregnancy and after delivery. The concentration of this a,-globulin in most women was found to increase rapidly at the end of the first trimester. In the third trimester the average concentration was more stable around 100 mg. per 100 ml. After delivery there was a rapid decrease, and 6 weeks post partum no women had concentrations exceeding 10 mg. per 100 ml. The possibility that PZ is involved in immunoregulatory mechanisms during pregnancy is discussed.
THE
‘ ’ P R E G N A N C Y
Z 0 N E ’ ’
PrOteiIl
(PZ) is an a,-globulin of unknown origin and function occurring in the sera of women during pregnancy. Smithies,’ using starch gel electrophoresis, found an extra protein zone in the sera of some pregnant women which disappeared after delivery. This original observation has been followed by reports from other authorszeR PZ at first was thought to be specific for pregnancy but has later been found also in women receiving oral contraceptive? 9. In and in men when treated with estrogen for prostatic cancer.“, I1 There have aIso been reports on various a,-globulins with characteristics similar to those of PZ as PAG ‘2 Xh >‘3 ‘$? and L ,I>(j cyL_pregnoglobulin,” the pregnancy-associated plasma proteins From the Department Gynaecology, University
of Obstetrics of Umea”.
Supported Research 4217-01) University
by the Swedish Council (Project and the Medical of Umed.
Received 1973.
for publication
Accepted
December
and
Medical B74-13XFaculty, Nouember
21,
31, 1973.
Reprint requests: Dr. Bo von Schoultz, Department of Obstetrics and Gynecology, University of Umed, S-901 8.5 Umea”, Sweden.
(PAPP’s) .I5 Recently, an a2-macroglobulin associated with pregnancy and with a molecular weight of 506,000 has been iso1ated.l” PZ has been purified and has been found to have a molecular weight of 326,000.‘7 After purification, a precipitating rabbit antiserum was prepared against PZ,l” and by means of this reagent the presence of PZ was studied by double diffusion according to Ouchterlony’” in some clinical investigations. PZ seems confined to the maternal circulation, since it has not been found in the cord blood, placenta, or amniotic fluid.18 At term pregnancy, PZ was detected in 90 per cent of the sera from 350 pregnant women.2o Lack of PZ at term did not seem to affect fetal welfare. On the other hand, in early pregnancy PZ was found much more rarely and in smaller amounts in a group of women with spontaneous abortions than in women with normal pregnancies of comparable gestational length.*l Recently, purified PZ was found to inhibit the lymphocyte response to phytohemagglutinin (PHA) stimulation.2” The purification of the PZ has made it possible to develop an immunologic method for quantitative measurement. The present
Volume Number
Pregnancy
119 6
n:2~ weeks
9
of gestation
zone protein
in pregnant
and puerperal
women
793
13 nndlL
I 1 0
20
9
LO 60
n-50
n
1 1 n ry 100 120 140 160 180 zoo 220 2LO 260 280
80
weeksof
n=&
weeks
gesta!
on
39and
33
20
Fig. 1. Distribution serum concentration
1
22222
and
LO
LO 60
3
I 80
1 100 120
IL0 160 180200
2202LO
260280
: 300
mg
of individual women in a total of 72 primigravidas of PZ in various gestational weeks.
work describes quantitative variations of PZ in the sera of women during pregnancy and after delivery. Material
/ lOOmi
5 1, 7 22
0
m9
25and26
of gestation
5
300
methods
A total of 860 blood samples were drawn from 72 women during pregnancy and after delivery. The blood samples were collected without anticoagulant. After coagulation, the serum was decanted and stored at -20° C. until use. All sera were coded and tested blindly. All women were healthy primigravidas. They had never received oral contraceptive drugs. Between 5 and 15 samples were obtained from each woman. Monthly samples were collected in the first half of pregnancy, thereafter approximately every 2 weeks until term. After delivery, 3 samples were taken: at one day, one week, and finally 6 to 14 weeks post partum. Gestational length was estimated as the number of days from the last menstruation
I lOOmI
with respect to the
and by repeated gynecologic examinations. Data concerning the pregnancy and delivery were obtained from the medical records. PZ was measured quantitatively by single radial immunodiffusion.232 24 Glass slides with a 1 mm. thick layer of 1 per cent Agarose” containing 1 per cent monospecific rabbit were used. Circular wells anti-PZ serumI with a diameter of 3.9 mm. were cut in the gel and filled with 10 ,~l of undiluted serum samples to be tested. The slides were kept in a moist chamber at room temperature for 48 hours, and thereafter no further expansion of the precipitate rings could be observed. The protein content of a pure fraction of PZ17 was determined according to Lowry and associateq2s and this sample of pure PZ was used to calibrate a standard serum used throughout the investigation. In order to examine the reproducibility of *Behringwerke.
July 15, 1974 41x1. J. Obstet. Gynecol.
794 von Schoultz
PZ mg/lOOml
I
l
8 Weeks
Fig.
of
2. Variation
Per cent
IO
12
li,
16
18
20
22
concentration
PZ >img/lOOml
90.. 80 .. 70. 60.50.-
30..
20. I i, L Weeks
8
: 12
16
: : 20
26
28
30
32
X
36
38
LO
12
gestation
in the serum
IO01
10.~
2~
: 2L
: 28
32
36
:
of PZ in 5 primigravidas
during
pregnancy.
respectively. To estimate the influence of viscosity, one strum sample was diluted with 6 parts of saline or serum, respectively, from a healthy male blood donor. The mean values of d.’ and S.D. from 8 tests on the same slide were 87.67 f 2.23 and 87.21 t 3.15, respectively. A PZ concentration below 0 to 2 mg. per 100 ml. was found to give no visible precipitate. Concentrations of 2 to 4 mg. per 100 ml. of PZ gave precipitates tnostly too small and faint for accurate measurement.
LO
of gestation
Fig. 3. Detectability of PZ in the sera of 72 primigravidas during pregnancy. The detectability is expressed as the per rent of women with a PZ concentration exceeding 4 mg. per 100 ml. The number of women investigated at each time is indicated. The value for gestational Weeks 9 to 10 is based on data from 4 women only.
the method, one serum sample from a pregnant woman was tested 14 times on the same slide. The mean value of the square diameter (d.‘) was 93.42 with a standard deviation (SD.) of 2.57. Another serum sample was applied on 25 different slides, and the corresponding figures lvere 112.50 and 5.20,
Results In general, the concentration of PZ was found to increase with gestational length (Fig. 1 1, but there \vere considerable individual variations (Fig. 2) Variations during pregnancy in the frequency of individuals with a measurable amount of PZ is shown for the whole group in Fig. 3. In 9 of 72 women. the PZ was not found in measurable amounts (> 4 mg. per 100 ml.) during the whole pregnancy or after delivery. In this group, 10.5 samples \\rre studied altogether, and each woman was tested between 9 and 13 times.
In
the
63
women
producing
increasing
Volume Number
119 6
Pregnancy
zone
protein
in
pregnant
and
puerperal
women
795
PZ mg / 100rnl
/
120 110
A 10
4 Weeks
8 or
12
16
20
24
28
32
36
40
P
gesrarlo"
Fig. 4. Mean concentration of PZ in sera of the 63 primigravidas amounts of this protein at some time during pregnancy (A) or after
amounts of PZ during pregnancy, the concentrations began to rise in gestational Weeks 8 to 12, and in the third trimester of pregnancy a rather stable average level was reached (Table I). The average level of PZ in the third trimester was about 100 mg. per 100 ml. (Fig. 4, A). After delivery there was a rapid decrease, and 6 weeks post partum no woman had values exceeding 10 mg. per 100 ml. (Fig. 4, B). The level of PZ was subject to considerable individual variation which is reflected in high values of the standard deviation in different gestational weeks. Most women reached the maximal concentration of PZ in the last month of pregnancy or just after delivery. However, maximal values were obtained in 6 women in gestational Week 30 and in 2 women as early as in the twenty-third week of gestation (Fig. 5). Three women had toxemia of pregnancy, and one had mild diabetes. One woman was delivered in the thirtieth week of a dead child with severe malformations. One child died 3 days post partum from respiratory complications. Two women were delivered of twins. In all these women PZ was found in measurable amounts which did not differ significantly from average levels.
4
Weeks
20
22
Weeks
2L
who delivery
26
28
30
8
after
12
delivery
produced measurable (B) (Table I).
32
3~
36
38
LO
42 P ,.Y ,1 0,
ot gestation
Fig. 5. Distribution of individual women with respect to the time when the maximal concentration of PZ was found. Only the 63 women producing PZ in measurable amounts are included.
The 9 women with no detectable increase of PZ were delivered of healthy babies with normal birth weights ranging between 2,850 and 4,150 grams. One woman showed very high PZ values with a maximum of 302 mg. per 100 ml. in gestational Week 34 which is more than 3 S.D.U. higher than the mean maximal value. She was hospitalized in gestational Week 14 to 15 for imminent abortion. Comment
Previously there have been few quantitative studies of pregnancy proteins. An estimate of the level of SPR, a pregnancy-associ-
796
July 15, 1974 Am. J. Obstet. Gynecol.
von Schoultz
Table I. Mean and standard deviation for the serum concentration (milligrams per 100 ml.) of PZ during pregnancy and after delivery in the 63 primigravidas producing this protein in measurable amounts 1 Week
of gestation 9-10
11-13 13-14 15-16 17-18 19-20 ‘l-2:! 23-24 25-26 27-28 29-30 31-32 33-34 35-36 37-38 39-40 41-42
No.
4 17 21 21 ‘I? -.L “5 29 36 44 42 50 50 55 56 46 43 20
1 Mean
2.5 9.5 44.9 39.2 59.6 69.4 70.0 82.9 94.7 97.2 100.5 107.2 101.2 105.6 96.2
109.3 119.8
\
S.D. 1.0
10.0 38.8 36.1 40.2 43.9 47.7 55.9 51.0 53.9 54.7 46.2 56.3 56.4 51.7 59.1 42.9
Post partum
1 day 1 wk. 6-7 wk. 8-9 wk. lo-11 wk. 12-13 wk. 14-15 wk.
59
60 1 13 18 “0 3
104.3 85.6 3 2.1 3.5 2.9 1
50.2 48.0 1.0 2.7 2.2 0
ated az-globulin which may be identical with PZ, was made by BohnG in a small series of 8 pregnant women. The values ranged between 15 and 30 mg. per 100 ml. Bayer and KadachzG made quantitative estimates of a pregnancy-associated a,-globulin. In the present study, the serum concentration of PZ was measured quantitatively with an immunologic technique, and purified PZ was used to calibrate a standard serum. There seem to be individual variations in the ability to produce PZ. In a previous study of 350 women at term pregnancy,‘” about 10 per cent of the pregnant women did not develop measurable amounts of PZ. In agreement with this observation, 9 of the 72 primigravidas examined in this study were found to have amounts of PZ below 4 mg. per 100 ml. during the entire
pregnancy. Whether some individuals lack PZ totally or if PZ is present but in a very low concentration, which seems more likely, can be settled only after studies with more sensitive techniques, i.e., radioimmunoassay. Among the women who produced measurable amounts of PZ, a marked individual \,ariation was found as illustrated by the data for the 5 individual women shown in Fig. 2. In general, a successive increase in concentration with gestational length was found (Fig. I), but there were considerable fluctuations up and down and in some women, for instance, No. 39. (Fig. 2), a decrease was found during the last month of pregnancy. The increase of PZ started by the end of the first trimester, and between gestational Weeks 8 and 12 the frequency of individuals with detectable PZ was rising rapidly to reach a rather stable level of about 90 per cent detectability (Fig. 3) in the last half of pregnancy. Also the shape of the curve in Fig. 4, A, indicates a more rapid increase in gestational Weeks 8 to 12 than later in pregnancy. In the third trimester of pregnancy, the mean serum concentration of PZ was stable around 100 mg. per 100 ml. After delivery there was a rapid decrease in the serum concentration of PZ, and after 6 weeks no values exceeding 10 mg. per 100 ml. Lvere found. The half time value for PZ seems to be around 3 to 4 weeks. This disappearance rate is in agreement with previous observations.“1 The levels of many serum proteins show moderate alterations during pregnancy.2i However, the increase of PZ is very pronounced, 10 to 50 times the level among nonpregnant women. The increase of PZ is unlikely to represent a nonspecific adjustment mechanism but rather a phenomenon with a specific function during a normally progressing pregnancy. Individual ability to produce PZ is necessary; furthermore, the presence of estrogen in a sufficient amount seems important for the production of Pz.l”, I1 However, according to prelim-
Vohlme Kumber
119 6
Pregnancy
inary data there is no correlation between the estrogen levels and the concentration of PZ. Absence of PZ at term pregnancy does not seem to interfere with fetal welfare,‘O while absence of PZ during the 9 to 12 weeks of pregnancy has been found to be associated with a high risk for spontaneous abortion.21 It is notable that in the period when spontaneous abortions are frequent a rapid increase in the serum level of PZ is observed. Immunologic tolerance from the mother versus the fetus, which can be looked upon as an allograft, is a necessary prerequisite for a normal pregnancy. Kasakura** has reported the presence of an immunosuppressive factor in pregnancy plasma. The nature of this factor, which is found in increased amounts with increased gestational length, is unknown. Sera from women receiving
REFERENCES
1. Smithies, 1959. 2. 3.
4. 5. 6. 7. 8.
9. 10.
11. 12.
13. 14. 15.
protein
Protein
Chem.
in pregnant
and
puerperal
women
797
oral contraceptive drugs have been shown to have an immunosuppressive effect.2Q The recent observation that purified PZ inhibits the lymphocyte response to PHA stimulation suggests that this protein is involved in the immunoregulatory mechanisms during pregnancy.22 One may speculate whether the individual variations in the level of PZ may reflect not only differences in the ability to produce this protein but also variations in the need for its biological effect. According to this hypothesis, one might expect a higher serum level of PZ in mothers with genetically incompatible fetuses. I wish to express my gratitude to Professors L. Beckman and P. LundstrGm for stimulating criticism and support during the investigation and to Professor S. Holm and Dr. R. BrGnnestam for valuable advice concerning the immunological technique. Skillful technical assistance was provided by Miss B. Israelsson and Mrs. M. Isaksson.
16.
0. : A&.
14: 65,
Stimson,
W.
H.,
and
Eubank-Scott,
L.:
F. E. B. S. Lett. 23: 298, 1972. 17.
de Alvarez, R. R.: AM. J. OBSTET. GYNECOL. 86: 815, 1963. Studd, J. W., Blainey, J. D., and Bailey, D. E.: J. Obstet. Gynaecol. Br. Commonw. 77: 42, 1970. Margolis, J., and Kenrick, K. G.: J. Exp. Biol. Med. Sci. 47: 637, 1969. Cooper, D. W.: Nature 200: 892, 1963. Bohr-r, H.: Arch. Gynaekol. 210: 440, 1971. Wilken, H.: Arch. Gynaekol. 199: 243, 1963. Hofman, R., Straube, W., Klausch, B., Frimel, H., and Giinther, J.: Arch. Gynaekol. 212: 246, 1972. Afonso, J. F., and de Alvarez, R. R.: Pa. Med. 70: 43, 1967. Beckman, L., von Schoultz, B., and Stigbrand, T.: Acta Obstet. Gynecol. Stand. 50: 369, 1971. Beckman, L., von Schoultz, B., and Stigbrand, T.: Urol. Res. 1: 67, 1973. MacLaren, J. A., Thornes, R. D., Roby, c. c., and Reid, D. E.: AM. J. OBSTET. GYNECOL. 78: 939, 1959. Bundschuh, G.: Acta Biol. Med. Ger. 17: 349, 1966. Berne, B.: Fed. Proc. 32: 677, 1973. Lin, T. M., Halbert, S. P., and Kiefer, D.: Fed. Proc. 32: 623, 1973. Afonso,
zone
J. F., and
18.
19. 20.
21.
22. 23. 24. “5.
36. 27.
28. 29.
van Schoultz, B., and Stigbrand, T.: Acta Obstet. Gynecol. Stand. 52: 51, 1973. Beckman, L., von Schoultz, B., and Stigbrand, T.: Acta Obstet. Gynecol. Stand. 52: 157, 1973. Ouchterlony, 0. : Acta Pathol. Microbial. Stand. 25: 186, 1948. Beckman, G., von Schoultz, B., and Stigbrand, T.: Acta Obstet. Gynecol. Stand. 53: 59, 1974. Beckman, G., Beckman, L., Magnusson, S., and von Schoultz, B.: Acta Obstet. Gynecol. Stand. 53: 177, 1974. von Schoultz, B., Stigbrand, T., and Tarnvik, A.: F. E. B. S. Lett. 38: 23, 1973. Mancini, G., Carbonara, A. O., and Here21 235, 1965. mans, J. F.: Immunochemistry StGriko. K.: Blut 16: 200. 1968. Lowry,‘O. H., Rosebrough,’ N. J., Farr, A. L., and Randall, R. J.: J. Biol. Chem. 193: 265, 1951. Bayer, H., and Kadach, D.: Zentralbl. Gynaekol. 92: 1201, 1970. Hytten, F. E., and Leitch, I.: The Physiology of Human Pregnancy, ed. 2, Oxford, 1971, Blackwell Scientific Publications, p. 47. Kasakura, S.: J. Immunol. 107: 1296, 1971. Hagen, C., and Frb;land, A.: Lancet 1: 1185, 1972.
study of the pregnancy zone
protein in the sera of pregnant and puerperal women BO
VON
Umea”,
SCHOULTZ
Sweden
The serum concentration of the pregnancy zone protein (PZ) was measured by means of single radial immunodiffusion in 72 primigravidas who were followed during pregnancy and after delivery. The concentration of this a,-globulin in most women was found to increase rapidly at the end of the first trimester. In the third trimester the average concentration was more stable around 100 mg. per 100 ml. After delivery there was a rapid decrease, and 6 weeks post partum no women had concentrations exceeding 10 mg. per 100 ml. The possibility that PZ is involved in immunoregulatory mechanisms during pregnancy is discussed.
THE
‘ ’ P R E G N A N C Y
Z 0 N E ’ ’
PrOteiIl
(PZ) is an a,-globulin of unknown origin and function occurring in the sera of women during pregnancy. Smithies,’ using starch gel electrophoresis, found an extra protein zone in the sera of some pregnant women which disappeared after delivery. This original observation has been followed by reports from other authorszeR PZ at first was thought to be specific for pregnancy but has later been found also in women receiving oral contraceptive? 9. In and in men when treated with estrogen for prostatic cancer.“, I1 There have aIso been reports on various a,-globulins with characteristics similar to those of PZ as PAG ‘2 Xh >‘3 ‘$? and L ,I>(j cyL_pregnoglobulin,” the pregnancy-associated plasma proteins From the Department Gynaecology, University
of Obstetrics of Umea”.
Supported Research 4217-01) University
by the Swedish Council (Project and the Medical of Umed.
Received 1973.
for publication
Accepted
December
and
Medical B74-13XFaculty, Nouember
21,
31, 1973.
Reprint requests: Dr. Bo von Schoultz, Department of Obstetrics and Gynecology, University of Umed, S-901 8.5 Umea”, Sweden.
(PAPP’s) .I5 Recently, an a2-macroglobulin associated with pregnancy and with a molecular weight of 506,000 has been iso1ated.l” PZ has been purified and has been found to have a molecular weight of 326,000.‘7 After purification, a precipitating rabbit antiserum was prepared against PZ,l” and by means of this reagent the presence of PZ was studied by double diffusion according to Ouchterlony’” in some clinical investigations. PZ seems confined to the maternal circulation, since it has not been found in the cord blood, placenta, or amniotic fluid.18 At term pregnancy, PZ was detected in 90 per cent of the sera from 350 pregnant women.2o Lack of PZ at term did not seem to affect fetal welfare. On the other hand, in early pregnancy PZ was found much more rarely and in smaller amounts in a group of women with spontaneous abortions than in women with normal pregnancies of comparable gestational length.*l Recently, purified PZ was found to inhibit the lymphocyte response to phytohemagglutinin (PHA) stimulation.2” The purification of the PZ has made it possible to develop an immunologic method for quantitative measurement. The present
Volume Number
Pregnancy
119 6
n:2~ weeks
9
of gestation
zone protein
in pregnant
and puerperal
women
793
13 nndlL
I 1 0
20
9
LO 60
n-50
n
1 1 n ry 100 120 140 160 180 zoo 220 2LO 260 280
80
weeksof
n=&
weeks
gesta!
on
39and
33
20
Fig. 1. Distribution serum concentration
1
22222
and
LO
LO 60
3
I 80
1 100 120
IL0 160 180200
2202LO
260280
: 300
mg
of individual women in a total of 72 primigravidas of PZ in various gestational weeks.
work describes quantitative variations of PZ in the sera of women during pregnancy and after delivery. Material
/ lOOmi
5 1, 7 22
0
m9
25and26
of gestation
5
300
methods
A total of 860 blood samples were drawn from 72 women during pregnancy and after delivery. The blood samples were collected without anticoagulant. After coagulation, the serum was decanted and stored at -20° C. until use. All sera were coded and tested blindly. All women were healthy primigravidas. They had never received oral contraceptive drugs. Between 5 and 15 samples were obtained from each woman. Monthly samples were collected in the first half of pregnancy, thereafter approximately every 2 weeks until term. After delivery, 3 samples were taken: at one day, one week, and finally 6 to 14 weeks post partum. Gestational length was estimated as the number of days from the last menstruation
I lOOmI
with respect to the
and by repeated gynecologic examinations. Data concerning the pregnancy and delivery were obtained from the medical records. PZ was measured quantitatively by single radial immunodiffusion.232 24 Glass slides with a 1 mm. thick layer of 1 per cent Agarose” containing 1 per cent monospecific rabbit were used. Circular wells anti-PZ serumI with a diameter of 3.9 mm. were cut in the gel and filled with 10 ,~l of undiluted serum samples to be tested. The slides were kept in a moist chamber at room temperature for 48 hours, and thereafter no further expansion of the precipitate rings could be observed. The protein content of a pure fraction of PZ17 was determined according to Lowry and associateq2s and this sample of pure PZ was used to calibrate a standard serum used throughout the investigation. In order to examine the reproducibility of *Behringwerke.
July 15, 1974 41x1. J. Obstet. Gynecol.
794 von Schoultz
PZ mg/lOOml
I
l
8 Weeks
Fig.
of
2. Variation
Per cent
IO
12
li,
16
18
20
22
concentration
PZ >img/lOOml
90.. 80 .. 70. 60.50.-
30..
20. I i, L Weeks
8
: 12
16
: : 20
26
28
30
32
X
36
38
LO
12
gestation
in the serum
IO01
10.~
2~
: 2L
: 28
32
36
:
of PZ in 5 primigravidas
during
pregnancy.
respectively. To estimate the influence of viscosity, one strum sample was diluted with 6 parts of saline or serum, respectively, from a healthy male blood donor. The mean values of d.’ and S.D. from 8 tests on the same slide were 87.67 f 2.23 and 87.21 t 3.15, respectively. A PZ concentration below 0 to 2 mg. per 100 ml. was found to give no visible precipitate. Concentrations of 2 to 4 mg. per 100 ml. of PZ gave precipitates tnostly too small and faint for accurate measurement.
LO
of gestation
Fig. 3. Detectability of PZ in the sera of 72 primigravidas during pregnancy. The detectability is expressed as the per rent of women with a PZ concentration exceeding 4 mg. per 100 ml. The number of women investigated at each time is indicated. The value for gestational Weeks 9 to 10 is based on data from 4 women only.
the method, one serum sample from a pregnant woman was tested 14 times on the same slide. The mean value of the square diameter (d.‘) was 93.42 with a standard deviation (SD.) of 2.57. Another serum sample was applied on 25 different slides, and the corresponding figures lvere 112.50 and 5.20,
Results In general, the concentration of PZ was found to increase with gestational length (Fig. 1 1, but there \vere considerable individual variations (Fig. 2) Variations during pregnancy in the frequency of individuals with a measurable amount of PZ is shown for the whole group in Fig. 3. In 9 of 72 women. the PZ was not found in measurable amounts (> 4 mg. per 100 ml.) during the whole pregnancy or after delivery. In this group, 10.5 samples \\rre studied altogether, and each woman was tested between 9 and 13 times.
In
the
63
women
producing
increasing
Volume Number
119 6
Pregnancy
zone
protein
in
pregnant
and
puerperal
women
795
PZ mg / 100rnl
/
120 110
A 10
4 Weeks
8 or
12
16
20
24
28
32
36
40
P
gesrarlo"
Fig. 4. Mean concentration of PZ in sera of the 63 primigravidas amounts of this protein at some time during pregnancy (A) or after
amounts of PZ during pregnancy, the concentrations began to rise in gestational Weeks 8 to 12, and in the third trimester of pregnancy a rather stable average level was reached (Table I). The average level of PZ in the third trimester was about 100 mg. per 100 ml. (Fig. 4, A). After delivery there was a rapid decrease, and 6 weeks post partum no woman had values exceeding 10 mg. per 100 ml. (Fig. 4, B). The level of PZ was subject to considerable individual variation which is reflected in high values of the standard deviation in different gestational weeks. Most women reached the maximal concentration of PZ in the last month of pregnancy or just after delivery. However, maximal values were obtained in 6 women in gestational Week 30 and in 2 women as early as in the twenty-third week of gestation (Fig. 5). Three women had toxemia of pregnancy, and one had mild diabetes. One woman was delivered in the thirtieth week of a dead child with severe malformations. One child died 3 days post partum from respiratory complications. Two women were delivered of twins. In all these women PZ was found in measurable amounts which did not differ significantly from average levels.
4
Weeks
20
22
Weeks
2L
who delivery
26
28
30
8
after
12
delivery
produced measurable (B) (Table I).
32
3~
36
38
LO
42 P ,.Y ,1 0,
ot gestation
Fig. 5. Distribution of individual women with respect to the time when the maximal concentration of PZ was found. Only the 63 women producing PZ in measurable amounts are included.
The 9 women with no detectable increase of PZ were delivered of healthy babies with normal birth weights ranging between 2,850 and 4,150 grams. One woman showed very high PZ values with a maximum of 302 mg. per 100 ml. in gestational Week 34 which is more than 3 S.D.U. higher than the mean maximal value. She was hospitalized in gestational Week 14 to 15 for imminent abortion. Comment
Previously there have been few quantitative studies of pregnancy proteins. An estimate of the level of SPR, a pregnancy-associ-
796
July 15, 1974 Am. J. Obstet. Gynecol.
von Schoultz
Table I. Mean and standard deviation for the serum concentration (milligrams per 100 ml.) of PZ during pregnancy and after delivery in the 63 primigravidas producing this protein in measurable amounts 1 Week
of gestation 9-10
11-13 13-14 15-16 17-18 19-20 ‘l-2:! 23-24 25-26 27-28 29-30 31-32 33-34 35-36 37-38 39-40 41-42
No.
4 17 21 21 ‘I? -.L “5 29 36 44 42 50 50 55 56 46 43 20
1 Mean
2.5 9.5 44.9 39.2 59.6 69.4 70.0 82.9 94.7 97.2 100.5 107.2 101.2 105.6 96.2
109.3 119.8
\
S.D. 1.0
10.0 38.8 36.1 40.2 43.9 47.7 55.9 51.0 53.9 54.7 46.2 56.3 56.4 51.7 59.1 42.9
Post partum
1 day 1 wk. 6-7 wk. 8-9 wk. lo-11 wk. 12-13 wk. 14-15 wk.
59
60 1 13 18 “0 3
104.3 85.6 3 2.1 3.5 2.9 1
50.2 48.0 1.0 2.7 2.2 0
ated az-globulin which may be identical with PZ, was made by BohnG in a small series of 8 pregnant women. The values ranged between 15 and 30 mg. per 100 ml. Bayer and KadachzG made quantitative estimates of a pregnancy-associated a,-globulin. In the present study, the serum concentration of PZ was measured quantitatively with an immunologic technique, and purified PZ was used to calibrate a standard serum. There seem to be individual variations in the ability to produce PZ. In a previous study of 350 women at term pregnancy,‘” about 10 per cent of the pregnant women did not develop measurable amounts of PZ. In agreement with this observation, 9 of the 72 primigravidas examined in this study were found to have amounts of PZ below 4 mg. per 100 ml. during the entire
pregnancy. Whether some individuals lack PZ totally or if PZ is present but in a very low concentration, which seems more likely, can be settled only after studies with more sensitive techniques, i.e., radioimmunoassay. Among the women who produced measurable amounts of PZ, a marked individual \,ariation was found as illustrated by the data for the 5 individual women shown in Fig. 2. In general, a successive increase in concentration with gestational length was found (Fig. I), but there were considerable fluctuations up and down and in some women, for instance, No. 39. (Fig. 2), a decrease was found during the last month of pregnancy. The increase of PZ started by the end of the first trimester, and between gestational Weeks 8 and 12 the frequency of individuals with detectable PZ was rising rapidly to reach a rather stable level of about 90 per cent detectability (Fig. 3) in the last half of pregnancy. Also the shape of the curve in Fig. 4, A, indicates a more rapid increase in gestational Weeks 8 to 12 than later in pregnancy. In the third trimester of pregnancy, the mean serum concentration of PZ was stable around 100 mg. per 100 ml. After delivery there was a rapid decrease in the serum concentration of PZ, and after 6 weeks no values exceeding 10 mg. per 100 ml. Lvere found. The half time value for PZ seems to be around 3 to 4 weeks. This disappearance rate is in agreement with previous observations.“1 The levels of many serum proteins show moderate alterations during pregnancy.2i However, the increase of PZ is very pronounced, 10 to 50 times the level among nonpregnant women. The increase of PZ is unlikely to represent a nonspecific adjustment mechanism but rather a phenomenon with a specific function during a normally progressing pregnancy. Individual ability to produce PZ is necessary; furthermore, the presence of estrogen in a sufficient amount seems important for the production of Pz.l”, I1 However, according to prelim-
Vohlme Kumber
119 6
Pregnancy
inary data there is no correlation between the estrogen levels and the concentration of PZ. Absence of PZ at term pregnancy does not seem to interfere with fetal welfare,‘O while absence of PZ during the 9 to 12 weeks of pregnancy has been found to be associated with a high risk for spontaneous abortion.21 It is notable that in the period when spontaneous abortions are frequent a rapid increase in the serum level of PZ is observed. Immunologic tolerance from the mother versus the fetus, which can be looked upon as an allograft, is a necessary prerequisite for a normal pregnancy. Kasakura** has reported the presence of an immunosuppressive factor in pregnancy plasma. The nature of this factor, which is found in increased amounts with increased gestational length, is unknown. Sera from women receiving
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oral contraceptive drugs have been shown to have an immunosuppressive effect.2Q The recent observation that purified PZ inhibits the lymphocyte response to PHA stimulation suggests that this protein is involved in the immunoregulatory mechanisms during pregnancy.22 One may speculate whether the individual variations in the level of PZ may reflect not only differences in the ability to produce this protein but also variations in the need for its biological effect. According to this hypothesis, one might expect a higher serum level of PZ in mothers with genetically incompatible fetuses. I wish to express my gratitude to Professors L. Beckman and P. LundstrGm for stimulating criticism and support during the investigation and to Professor S. Holm and Dr. R. BrGnnestam for valuable advice concerning the immunological technique. Skillful technical assistance was provided by Miss B. Israelsson and Mrs. M. Isaksson.
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