Cong. Anom., 32: 301-307, 1992

Review

Systemic Lupus Erythematosus and Congenital Anomalies, Focusing

on Neonatal Lupus Erythematosus and Anti-SS-NSS-B Antibodies*

Hiroshi HASHIMOTO, Yoshinari TAKASAKI and Kaoru HIROKAWA Juntendo University, School of Medicine, Department of Internal Medicine and Rheumatology, 2-1-1, Hongo, Bunkyo-ku, Tokyo 113, Japan

ABSTRACT SLE is a representative autoimmune disease which develops preferentially in women of childbearing age. Its frequent occurrence makes the coincidence of SLE and pregnancy an important clinical problem. SLE is thought to be multifactorial dis- ease. A familial prevalence was found to be 3% which was significantly higher when compared with Japanese prevalence of SLE. When women with SLE become pregnant, the fetus is at high risk and is adversely affected showing the high prevalence of fetal loss. Antiphospholipid antibodies were thought to be one of the causative factors. Ne- onetal lupus erythematosus (NLE) including lupus like skin lesions and congenital com- plete heart block (CCHB) is associated with maternal anti-SS-A and SS-B antibodies. The disease resolves with normalization of the maternal antibodies by the 8th month after delivery with the exception of the CCHB which is almost universally irriversible. When the sera from 4 maternal patients with NLE and 32 patients with normal delivery were analyzed by immunoblotting using recombinant 60 and 52 kD SS-A, and SS-B pu- rified from calf thymus extract, the frequency of anti-52 kD SS-A and SS-B in patients with NLE was significantly higher than that of patients with normal delivery. Anti-SS- A/SS-B antibodies may react with the SS-A/SS-B antigens in fetal heart tissue as fetal levels of IgG increases which is almost simultaneously as when the SS-A/SS-B antigens appear in the fetal heart tissue. The pathogenesis of tissue damage mediated by autoim- mune mechanisms specifically dependent on the biology of pregnancy is recognized to be due to passively acquired autoimmune injury. Key words: SLE, neonatal lupus erythematosus, congenital complete heart block, anti- SS-A antibodies, anti-SS-B antibodies.

INTRODUCTION

Systemic lupus erythematosus (SLE) is a representative autoimmune disease which develops preferen- tially in women of childbearing age. Its frequent occurrence makes the coincidence of SLE and pregnancy an important clinical problem. SLE is thought to be polygenic genetically and multifactorial disease. However,

Received August 20, 1992 * Presented in the “Symposium on Maternal Complications and Congenital Abnormalities” at the 32nd Annual

Meeting of the Japanese Teratology Society, Tokyo, July 10, 1992 1*#%!, WIXE, EJll H. lllBXFtk4B?25BE3%PJ$t, 7113 %E@*JXE*#V 2 TH 1-1

302 H. Hashimoto et al.

the familial occurrence of SLE is quite high showing a familial prevalence of 2 to 12% (Arnett, 1987). On the other hand, SLE patients have a lot of autoantibodies including antinuclear antibodies (ANA), antiphospholipid antibodies (aPL), Coombs antibodies and antiplatelet antibodies, etc. ANA includes ant- DNA antibodies, anti-Sm antibodies, anti-U1 -RNP antibodies, anti-SS-A antibodies (anti-SS-A), anti-SS- B antibodies (anti-SS-B), etc. The aPL includes anti-cardiolipin antibodies (aCL) and lupus anticoagulant (LAC) and false positive serological test for syphilis (STS). Among these autoantibodies, anti-SS-A and/or anti-SS-B, and aPL affect the neonatal outcome, if the maternal SLE patients have these antibodies. The former is associated with NLE including congenital complete heart block (CCHB) of the fetus and the latter is associated with spontaneous abortions and/or intrauterine death.

In this paper, genetic background concerning HLA antigens, familial occurrence of SLE and the out- come of children who were born to maternal SLE patients, prognosis of fetus in maternal SLE and NLE focusing CCHB and anti-SS-A/anti-SS-B were described.

GENETIC BACKGROUND

1. HLA antigens SLE develops within a complex network of genetic and immunologic factors which interactions consti-

tute the basis for the extensive heterogeneity that is characteristic of the syndrome. Among these factors is one or more HLA Class II specificity. Until now, both DR2 and DR3 are confirmed association with SLE (Arnett, 1987). Japanese SLE patients were associated with DR2 but not with DR3 due to lack of Japanese population with DR3 (Hashimoto et al., 1985). Recently detailed analysis of HLA antigens is possible using DNA typing. We tested HLA antigens in 58 Japanese SLE patients who fulfilled the ARA diagnostic criteria along with 100 normal controls. HLA class I and II antigens were typed serologically using the antisera provided by the 11th HLA Workshop. Concerning the HLA class II antigens, further DRB, DQ and DP alleles were defined by DNA typing using the PCR/SSO method. There were signifi- cantly more SLE patients with HLA-B39, DRBl * 1501, DRB*0101 and DQBl *Om2 than the normal controls. From this result, the haplotype of HLA-DRBI * 1501-DRB5 * 0101-DQA1*0102-DQB1*0602 was thought to be SLE-associated MHC markers in Japan.

2. Familial prevalence of SLE We (1991) sought positive family histories in 729 patients with SLE and documented a familial preva-

lence of 3% in which the rate was relatively lower than previously reported. There was a significant differ- ence compared with the rate of 6.6 to 8.5 per 100,OOO of Japanese prevalence of SLE. Females predominate with mother-daughter and sister-sister combinations being most common. Nonetheless, there may be an excess of males (approximately 20%) as compared to series of SLE patients where a fema1e:male ratio of 10: 1 usually found (Arnett, 1987). Block (1975) provided an excellent review of all 17 previously report- ed twin pairs and added 12 additional well-studied sets. Zygosity was proven in seven monozygous and three dizygous pairs. Four of the seven (57%) monozygotic twins were concordant for SLE, while three dizygous pairs were discordant for clinical SLE. These findings supported the genetic influences on the expression of SLE. However, the lack of 100% concordance in monozygotic twins implies the involvement of environmental factors.

Neonatal lupus and anti-SS-A/anti-SS-B 303

3. Offspring Outcome of Maternal SLE We studied the ANA in children who were born to the patients with SLE (Hashimoto, 1991). ANA was

found 10 out of 48 children (21%). ANA was detected in 2 out of 3 children within 5 months after birth. However, ANA could not be detected in the children between 6 months and 4 years of age. Five years after birth, 8 out of 22 children had ANA including anti-DNA and anti-cardiolipin in one child and anti- SS-A in another. Furthermore, 2 offsprings developed overt SLE. Thus, genetic factors were thought to be associated with the development of SLE. Lehman (1989) noted that the development of SLE in male children younger than 18 years of age, and in all children younger than age 10 at the time of diagnosis, strongly correlates with the presence of anti-SS-A in the mother’s serum. They also noted that the associa- tion of maternal anti-SS-A from transient “neonatal” SLE to SLE in childhood, and suggested that maternal anti-SS-A might be of fundamental importance in the pathogenesis of some cases of childhood SLE.

NEONATAL OUTCOME OF MATERNAL SLE

1. Prognosis of Fetus in Maternal SLE Prognosis of fetus in 192 pregnancies of 87 maternal SLE patients was studied subdividing pregnancy

before diagnosis of maternal SLE, diagnosis of maternal SLE during pregnancy, diagnosis of maternal SLE after delivery and pregnancy after diagnosis of maternal SLE (Hashimoto, 1989) (Table 1). Spon- taneous abortion was found in 11 To of the pregnancies after diagnosis of maternal SLE which coincides almost to those with pregnancy before onset of maternal SLE. On the other hand, intrauterine death was found in 12% of the pregnancies after diagnosis of maternal SLE. Thus, the fetus was at high risk and was adversely affected not only pregnancy after diagnosis of maternal SLE but also in pregnancy before diagnosis of maternal SLE. Furthermore, growth retardation occurred in the immediate neonatal period. Although the reasons for the high prevalence of fetal loss remain uncertain, aPL is thought to be associat- ed with spontaneous abortion, intrauterine death and fetal growth retardation (Table 2).

2. NLE and anti-SS-A/anti-SS-B 1) NLE

NLE is not well defined and the term has been commonly used to describe a baby born with discoid skin lesions. The designation now seems to have been extended to infants with not only discoid lesions but also lupus like rash, hemolytic anemia, thrombocytopenia and congenital heart block. Rarely, develop- ment of SLE is also observed. IgG class of autoantibodies including ANA, LE factors, Coombs antibodies and anti-platelet antibodies is detected in serum of infants as transplacental passage of maternal im- munoglobulin. Disease in the infants coincides with the presence of maternal antibodies in the fetal and neonatal circulation. However, the disease resolves with the normalization of the maternal antibodies by the 8th month after birth with the exception of CCHB which is almost universally irriversible (Buyon and Winchester, 1990).

2) SS-A and SS-B Antigens Recently, the structures of SS-A and SS-B antigens have been clarified. The gene that encodes 60-kD

(SS-A) antigen has been cloned (Ben-Chetrit et al., 1989). A second antigenically and structurally distinct polypeptide has been identified as a 52-kD (SS-A) species (Ben-Chetrit et al., 1988). Both of these SS-A

304

pregnancy diagnosis diagnosis pregnancy before of SLE of SLE after diagnosis during after diagnosis of SLE pregnancy delivery of SLE

n = 8 4 n = 7 n = 6 n = 95

Therapeutic abortion 8(10%) 1(14%) 1(17%) 19(20%)

Spontaneous abortion 8 (1 0 % ) 0 0 10(11%)

Intrauterine fetal death 1 ( 1%) 3(43%) 1(17%) 12(12%)

Premature delivery 2( 2%) 0 0 19(20%)

Normal delivery 65(77%) 3*(43%) 4**(67%) 35(37%)

H. Hashimoto et al.

Total

n = 192

29(15%)

1 8 ( 9%)

17 ( 9 % )

21 (11%)

107(56%)

Table 1

Prognosis of Pregnacy in SLE

Stillbirth Livebirth S.D.

Table 2

Fetal Prognosis and Autoantibodies in SLE

+ anti-UI-RNP -

anti-SS-A + -

1/6 (17) 5/6 (83) N.S. 11/17 (65) 6/17 (35)

3/13 (23) 10/13 (77) 5/17 (29) 12/17 (71) N.S.

anti-Sm 1 N.S. 1 8,220 (36) I 14/22 (64)

1/3 (33) I 2 /3 (67) I N.S. 1 9/28 (39) 19/28 (61) anti-SS-B

components are associated with 4 RNA species, designated hY1, hY3, hY4 and hY5. Another distinct 54-kD species has been identified in peripheral erythrocytes and is associated with only 2 RNA species (Rader et al., 1989). The 48-kD (SS-B) protein does not share the antigenic determinants with SS-A polypeptides. The SS-B component is more complex than the SS-A-associated RNAs, as well as to most RNA species transcribed by RNA polymerase III. Although the biologic function of SS-A particle asssembly is unknown, Gottlieb (1989) demonstrated the role of SS-B protein in the termination of transcription via the presumed induction of a conformational change in RNA polymerase III.

Neonatal lupus and anti-SS-A/anti-SS-B 305

Table 3

Neonatal LE and anti-SS-A Neonatal LE

1. CCHB (n=41)

2. CCHB+CLE (n= 2) CLE (n= 5)

3. CCHB (n= 2) CLE (n= 2)

Anti-SS-A

34 ( 83%)

2 (100%) 4 ( 80%)

2 (1 00%) 2 (1 00%)

Anti-SS-A I Neonatal LE

CLE 2 (8%) 4. connective tissue

diseases with anti-SS-A CLE 2 (7%)

5. 300 randomly selected (n= 3) mother-infant pair

CCHB: congenital complete heart block CLE: cutaneous LE

References

Scott, J.S., et al(1983)

Lee, L.A., et al(l983)

Hashimoto, et a1 (1992)

Hashimoto, H. et a1 (1992)

Hashimoto, H. et a1 (1992)

Calmes, M., et a1 (1985)

3 ) Frequency of NLE and Anti-SS-A It has been reported that the majority of infants with NLE are born to mothers with SLE/connective

tissue diseases and anti-SS-A (Table 3). Scott (1983) detected anti-SS-A in 34 of 41 mothers (83%) whose babies had CCHB. In our study, anti-SS-A was detected in all mothers whose babies had CCHB and/or cutaneous LE. On the other hand, Calmes (1985) studied the occurrence of detectable anti-SS-A and anti- SS-B in 300 randomly selected mother-infant pair. He noted that three mother-infant pairs ( 1 % ) were positive for anti-SS-A, no matched pair were positive for anti-SS-B, and the mother-infant pairs with anti-SS-A failed to reveal evidence of NLE. In our study, CCHB was observed in one out of 26 babies (4%) whose mothers had SLE and anti-SS-A, and in 2 out of 30 babies (7%) whose mothers had connective tissue diseases including SLE and Sjogren syndrome having anti-SS-A. Thus, prevalence of anti-SS-A is high in mothers whose babies had CCHB, and frequency of CCHB is low in babies whose mothers had anti-SS- A. However, the risk of anti-SS-A against CCHB is thought to be clear.

4) Relationship between NLE/CCHB and Anti-SS-A/Anti-SS-B Buyon (1990) studied the frequencies of anti-SS-A and anti-SS-B in women having offspring with and

without CCHB according to the previous reports. He recognized that anti-SS-A was present in over 85% of the sera from mothers of infants with CCHB. It was also noted that not only anti-SS-A but also anti- SS-B was strongly associated with the development of CCHB supporting that the vast predominance of anti-SS-B was found in association with anti-SS-A in many patients. We studied the relation of anti-SS-A and anti-SS-B to NLE in SLE patients using recombinant 60 kD and 52 kD SS-A antigens. Four patients with NLE and 32 patients with normal delivery were tested for anti-SS-A and anti-SS-B. Anti-SS-A and anti-SS-B were detected in 100% and 25% of patients with NLE and in 62.5% and 12.5% of patients with normal delivery by double immunodiffusion respectively. By enzyme linked immunosorbent assay using purified antigen from calf thymus extract, anti-SS-A and anti-SS-B were detected in 100% and 25% of

306 H. Hashimoto et al.

Table 4

lmmunoblot Analysis of Sera from Maternal SLE Patients

prevalence in patients

antibodies to with NLE without NLE n=4 n=32

60kD (SS-A) 4 (100) 30 ( 94) 52kD (SS-A) 3 ( 75)* 6 ( 19)* 48kD (SS-B) 3 ( 75)* 7 ( 22)*

60kD only 1 ( 25)** 29 ( go)** 60kD + 52kD 2 ( 50) 7 ( 22) 60kD + 48kD 3 ( 75) 7 ( 22) 60kD+52kD+48kD 2 ( 50) 2 ( 6)

( )Yo, * P<0.05, ** P<0.005

patients with NLE and 65.6% and 34.4% of parients with normal delivery respectively. Therefore there is no significant difference in those two groups. But when those sera were tested by immunoblotting using recombinant 60 and 52 kD SS-A, and SS-B purified from calf thymus extract, the frequency of anti-52 kD SS-A and SS-B in patients with NLE was significantly higher than that in parients with normal delivery (75% vs 18.8% and 75% vs 21.9%, respectively) (Table 4). In addition, it was shown that sera from pa- tients with NLE often had antibodies to 60 and 52 kD SS-A, and SS-B antibodies, and seldom had anti- bodies reactive only with 60 kD SS-A. These results suggested that immunoblotting using recombinant 60 and 52 kD SS-A was useful for the evaluation of determination for NLE/CCHB in maternal SLE.

5 ) Pathogenic Role of Maternal Anti-SS-A and Anti-SS-B in the Development of CCHB The clinical detection of CCHB would be expected to occur simultaneously with placental transport and

occur within the normal heart. According to Buyon (1990), bradycardia has been noted after an initially normal fetal heart rate, with problems developing after 16 weeks of gestation. Maternal antibodies inter- act with Fc receptors on the trophoblastic cell surface in a specific transport process. Fetal levels of IgG after 17 weeks of gestation steadily increase, reaching 400 mg/dl by the 24th week and 800 mg/dl by 32nd week (Stiehm, 1975). Although the human heart attains most of its adult characteristics by the 6th to 8th week of gestation (James, 1970), the fetal heart conduction system reaches functional maturity by the 16th week of gestation. On the other hand, Buyon (1989) demonstrated that the fetal heart tissue during the 18th-24th week of gestation contains readily detectable 48 kD SS-B antigen. In addition the 52 kD SS-A species is evident, although at lower levels, while still smaller quantities of the 60 kD SS-A polypeptide have been detected. Harley (1985) also noted that fetal heart during the 23rd week of gestation containes a greater quantity of SS-A per mg of protein than the hearts of the 18th-22nd week of gestation or an adult heart. There is a possibility that anti-SS-A and anti-SS-B might react to SS-A and SS-B antigens in the fetal heart tissue with simultaneous increase in the fetal IgG levels and the appearance of SS-A and SS-B antigens in the fetal heart tissue. Although it is uncertain that these antibodies react with fetal heart tissues directly, several investigators have demonstrated that the reactivity of sera with a monospecific anti-

Neonatal lupus and anti-SS-A/anti-SS-B 307

SS-A with fetal heart tissues, including the conduction system (Taylor et al., 1986, Deng et al., 1987), but the evidence of clear surface staining was lacking.

The pathogenesis of tissue damage mediated by autoimmune mechanisms specifically dependent o n the

biology of pregnancy is recognized to be due to passively acquired autoimmune injury (Buyon and Szer, 1986).

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