Maternal autoimmune response to recombinant Ro/SSA and La/SSB proteins in Japanese neonatal lupus erythem atosus

Juvenile-onset hypergammaglobulinemic purpura and fetal congenital heart block

Waldenström's hypergammaglobulinemic purpura (HGP) is a rare chronic disorder characterized by recurrent purpura on the legs, a polyclonal increase in serum gamma-globulin, an elevated erythrocyte sedimentation rate and a positive rheumatoid factor. A 30-year-old primigravid woman with 14 years of HGP was found to have fetal bradycardia at 25 weeks' gestation. Laboratory investigations demonstrated positive anti-Ro/SSA and anti-La/SSB antibodies in the maternal serum. Cesarean delivery was performed at 39 weeks, and a 2750-g female infant was born with complete atrioventricular block. Fortunately, the neonatal period has been uneventful without need for pace-making. Maternal HGP exacerbated just after delivery, but resolved within 1 week without treatment. Physicians should be aware of the possible presence of neonatal lupus-related anti-Ro/SSA and anti-La/SSB autoantibodies in patients with HGP. Screening for these autoantibodies is important and could be used as a marker to identify and manage high-risk pregnancies.

Immune responses to SS-A 52-kDa and 60-kDa proteins and to SS-B 50-kDa protein in mothers of infants with neonatal lupus erythematosus

Mothers who have anti-SS-A/Ro and anti-SS-B/La antibodies have a greater risk of bearing infants with neonatal lupus erythematosus (NLE). However, most mothers with anti-SS-A/Ro and anti-SS-B/La antibodies give birth to infants with no evidence of NLE. We studied mothers who had the combination of clinical evidence of connective tissue disorder, positive antinuclear antibody and positive anti-SS-A/Ro and/or anti-SS-B/La antibodies. We analysed SS-A/Ro and SS-B/La antibody responses to recombinant 60-, 52- and 50-kDa proteins in eight mothers of NLE infants and 19 mothers whose children did not have NLE. Molecular analysis of the anti-SS-A/Ro and anti-SS-B/La antibodies was carried out by enzyme-linked immunosorbent assay using recombinant 60-, 52- and 50-kDa proteins. The mothers of children with cutaneous NLE were all positive for a high titre of 50-kDa protein. Mothers of children with NLE with complete heart block (CHB) were positive for 52- and 60-kDa proteins. We conjecture that anti-SS-B/La antibody influences the development of cutaneous NLE, and that anti-SS-A/Ro antibody influences the development of NLE with CHB.

Keratinocytes from patients with lupus erythematosus show enhanced cytotoxicity to ultraviolet radiation and to antibody-mediated cytotoxicity

Keratinocyte cytotoxicity is an important component of the immunopathology of photosensitive lupus erythematosus, and antibody-dependent cell-mediated cytotoxicity (ADCC) has been shown to be an important mechanism by which autoantibodies, especially those specific for SS-A/Ro, can induce keratinocyte damage in models of photosensitive lupus. We provide further evidence that keratinocytes from patients with photosensitive lupus show significantly greater ultraviolet radiation (UVR)-induced cytotoxicity, and that ADCC of these targets is especially enhanced by autologous patient's serum or by anti-SS-A/Ro+ sera. Keratinocytes from normal uninvolved skin of 29 patients with cutaneous lupus erythematosus (LE) were grown in cell culture and tested as targets in cytotoxicity experiments in vitro. Cultured keratinocytes from patients with systemic lupus erythematosus (SLE) and subacute cutaneous lupus erythematosus (SCLE) showed significantly greater cytotoxicity following UVR treatment than did keratinocytes from normal adult controls or from neonatal foreskins (P < 0.01). The same cultures also showed greater UVR-induced binding of IgG from fractionated anti-SS-A/Ro+ preparations. ADCC experiments were also performed using keratinocytes cultured from patients with SLE, SCLE, discoid lupus erythematosus (DLE), and normal controls. When keratinocytes were incubated in autologous serum plus a standard mononuclear cell effector population, the percentage of ADCC observed was significantly greater in cultures containing keratinocytes and sera from the SLE and SCLE patients (P < 0.001). When cultured keratinocytes were added to different IgG antibody probes, plus standard mononuclear effector populations, greater ADCC was seen using the anti-SS-A/Ro probe and keratinocytes from patients with SLE or SCLE. With normal human neonatal keratinocyte targets, the anti-SS-A/Ro probe induced greater ADCC than that seen with anti-ssDNA or normal human serum. We have shown that keratinocytes from patients with some forms of lupus erythematosus (SLE and SCLE) show greater cytotoxicity in vitro when irradiated with UVR, and greater susceptibility to ADCC whether the antibody source is their own serum or an anti-SS-A/Ro probe.

Neonatal lupus erythematosus: maternal IgG antibodies bind to a recombinant NH2-terminal fusion protein encoded by human alpha-fodrin cDNA

IgG antibodies to a cleavage product of alpha-fodrin (120 kDa alpha-fodrin) have recently been identified as organ-specific autoantibodies in primary Sjögren's syndrome. In this study, we examined seroreactivity of mothers and infants with neonatal lupus erythematosus (NLE) to a recombinant NH2-terminal protein (120 kDa alpha-fodrin) of human alpha-fodrin. Serum samples were collected during the perinatal period in seven pregnancies of five mothers delivering offspring with NLE. Anti-120 kDa alpha-fodrin antibodies were identified by immunoblotting in six of seven perinatal maternal sera of offspring with NLE: one of two congenital heart block offspring and all five offspring with cutaneous NLE. These antibodies were placentally transmitted to infants. One of the five mothers had primary Sjögren's syndrome, and four were asymptomatic. One asymptomatic mother did not demonstrate anti-120 kDa alpha-fodrin activity at the time of the first delivery of a congenital heart block infant, but was found to be positive at the time of subsequent delivery of a second child with cutaneous NLE. We propose that maternal antibodies to 120 kDa alpha-fodrin may be an additional serologic marker for the risk of NLE in anti-Ro/SS-A positive women.

Polymorphisms of HLA class II genes and autoimmune responses to Ro/SS-A-La/SS-B among Japanese subjects

OBJECTIVE

To investigate HLA class II allele associations with autoantibody responses to Ro/SS-A and La/SS-B among Japanese subjects.

METHODS

Haplotype and allele distributions, along with molecular polymorphisms, of HLA class II genes were analyzed by polymerase chain reaction-restriction fragment length polymorphism in 41 Japanese women with precipitating autoantibodies to Ro/SS-A and/or La/SS-B.

RESULTS

Among women with both Ro/SS-A and La/SS-B antibodies, the HLA class II haplotype DRB1*08032/DQA1*0103/DQB1*0601 and DRB1*08032 allele showed significantly increased frequencies compared with patients with anti-Ro/SS-A alone or with normal controls. All women with both anti-Ro/SS-A and anti-La/SS-B, but not those with anti-Ro/SS-A alone, carried DRB1 alleles that shared the same amino acid residues at positions 14-31 and 71 of the hypervariable regions of the DRB1 chain. All anti-Ro/SS-A positive women carried 1 or 2 alleles of DQB1*06 and DQB1*03 subtypes that shared the same amino acid residues at positions 71-77 of the DQB1 chain. HLA class II allele distributions did not differ among 3 anti-Ro/SS-A positive groups with different disease expressions, i.e., patients with systemic lupus erythematosus, patients with primary Sjögren's syndrome, and women with no apparent symptoms of rheumatic disease.

CONCLUSION

HLA class II allele distributions differ among anti-Ro/SS-A positive subjects according to the presence or absence of coexisting anti-La/SS-B antibodies, but not according to disease expression. Our findings suggest that different HLA class II molecules might control the development of anti-Ro/SS-A and/or anti-La/SS-B antibodies in the autoimmune response to the Ro/SS-A-La/SS-B complex.

Neonatal lupus erythematosus: studies on HLA class II genes and autoantibody profiles in Japanese mothers

Neonatal lupus erythematosus (NLE) is a rare disorder of neonates characterized by two major clinical manifestations: congenital heart block and cutaneous lupus lesions. The disease is associated with placentally transferred maternal anti-Ro/SSA and/or La/SSB antibodies. To clarify possible class II HLA associations with maternal autoantibody responses, haplotypic and allelic distributions, along with the polymorphism of the MHC class II HLA alleles, were analyzed based on PCR-RFLP results in 25 Japanese mothers of two groups defined by precipitating autoantibody profiles. Among mothers with both anti-Ro/SSA and anti-La/SSB antibodies, but not those with anti-Ro/SSA alone, the class II haplotypes DRB1*1101-DQA1*0501-DQB1*0301 and DRB1*08032-DQA1*0103-DQB1*0601 as well as individual class II alleles DRB1*1101, DRB1*08032 and DQB1*0301 showed significantly increased frequencies compared to those in normal controls. All anti-Ro/SSA and anti-La/SSB positive mothers carried DRB1 alleles that shared the same amino acid residues at positions 14-31 and 71 of the DRB1 chain. These mothers also carried homozygous or heterozygous DQ6 and DQ3 alleles that shared the same amino acid residues at positions 27-36 and 71-77 of hypervariable regions of the DQB1 chain. Furthermore, all mothers with both anti-Ro/SSA and anti-La/SSB were homozygous for DPB1*0501. Nine of 10 anti-Ro/SSA and anti-La/SSB-positive mothers, but only 6 of 15 mothers with anti-Ro/SSA alone, had affected infants. Thus, our findings suggest that there may be immunogenetic differences among mothers according to their autoantibody profiles, and that mothers with both anti-Ro/SSA and anti-La/SSB are more likely to have infants with NLE than mothers with anti-Ro/SSA alone.