Clues to the aetiology and pathogenesis of herpes gestationis

Abnormal expression of class II MHC antigens in placentae from patients with pemphigoid gestationis: analysis of class II MHC subregion product expression

Abnormal expression of class II MHC antigens was consistently observed in an immunohistological study on placentae from patients with pemphigoid gestationis. The area affected in all the placentae was the chorionic villi adjacent to the maternal decidua. The villous stroma, and in some cases the chorionic fetal endothelium, had abnormal expression of class II MHC antigens. Monoclonal antibodies specific for the class II MHC subregion products (DR, DP and DQ) were used to analyse the class II MHC antigen expression. Differential expression of the class II MHC subregion products was observed on the villous stroma and chorionic fetal endothelium; DR and DP were always expressed but DQ in some cases was heterogeneous. This abnormal expression of class II MHC antigens may reflect an immunological attack on the placenta in pemphigoid gestationis.

Herpes gestationis

Only 14 years have elapsed since immunofluorescence techniques revised our concept of herpes gestationis. As our inquiry broadens, the answers seem farther away. Yet much knowledge has been gained regarding predisposition and the pathomechanism of this elusive disease. I offer a review of historical context and an update on our current confusions regarding this rare autoimmune dermatosis of pregnancy.

Bullous pemphigoid

Bullous pemphigoid is an autoimmune blistering dermatologic disease characterized clinically by tense bullae that may develop on normal or erythematous skin. The major histologic feature is a subepidermal blister with variable degrees of dermal inflammation. Other immunologically mediated blistering skin diseases may mimic bullous pemphigoid, including herpes gestationis, cicatricial pemphigoid, dermatitis herpetiformis, and epidermolysis bullosa acquisita. These diseases will be discussed. Most patients with bullous pemphigoid demonstrate circulating autoantibodies reactive with an antigen located in the lamina lucida region of the basement membrane zone. Complement activation by these autoantibodies initiates influx and activation of mast cells along with other inflammatory cells. Tissue injury with damage and eventual destruction of the basement membrane occurs as a result of the release of inflammatory mediators. The final result is subepidermal blister formation. The course of bullous pemphigoid tends to be self-limited, and successful treatment is usually effected with systemic glucocorticosteroids.

Perturbation of the immune network in herpes gestationis

We have studied the development of anti-idiotypic antibodies to HLA and of autoantibodies reacting with alloactivated T lymphoblasts in a woman with herpes gestationis (HG). This primigravida developed an elevated titer of anti-HLA antibodies, (Ab1), in association with a low titer and late appearance of anti-anti-HLA antibodies (Ab2). At delivery she developed only minimal levels of antibodies reacting with autologous T lymphoblasts (T1), sensitized against the immunizing HLA antigens of the child. Her serum reacted, however, with T lymphoblasts, primed in AMLC against autologous T blasts alloactivated in vitro against her husband (T2). Because healthy gravidae do not show such antibodies, it appears that they are peculiar to and may represent a perturbation of the idiotypic network in regard to the immune

Abnormal expression of HLA-DR antigen in the placenta of a patient with pemphigoid gestationis

The villous stroma and fetal endothelium in chorionic villi adjacent to maternal decidua in a placenta of a woman suffering from pemphigoid gestationis were found to have abnormal expression of HLA-DR antigen. This aberrant DR expression may be a reflection of an immune attack on the placenta.

Immunity in herpes gestationis: inhibition of mixed lymphocyte culture by patients' sera

The families of four patients with herpes gestationis (HG) (pemphigoid gestationis) and five patients with polymorphic eruption of pregnancy (PEP) were HLA typed. Anti-HLA-D antibodies in the maternal sera were sought using mixed lymphocyte culture (MLC) inhibition test. Two of the four patients with HG had Dw3, one of which was combined with Dw4. One of the fathers had Dw2. The sera of the four patients with HG strongly inhibited (48-100%) the MLC reaction of maternal cells against cells of the father or the child. This kind of inhibition could not be shown in the patients with PEP. We conclude that patients with HG often seem to have MLC inhibiting factors which obviously are antibodies directed against HLA-D region determinants. Their pathogenic role is still obscure.

The role of circulating immune complexes in the aetiology of polymorphic eruption of pregnancy

Circulating immune complexes were measured in 35 patients with polymorphic eruption of pregnancy employing three different techniques. No significant abnormalities were detected by the C1q solid phase binding assay and polyethylene glycol precipitation of immunoglobulin G. However, using a solid phase polyclonal rheumatoid factor binding assay, which detects small immune complexes, we demonstrated a significant reduction in the level of circulating immune complexes during the acute stage of the eruption. We suggest that the leakage of small immune complexes through dilated upper dermal vessels may play a role in the aetiology of polymorphic eruption of pregnancy.

The fetal prognosis in pemphigoid gestationis (herpes gestationis)

We have studied the infants in fifty pregnancies affected by pemphigoid gestationis (herpes gestationis). There was a significant increase in the frequency of infants that were 'small for dates'. As such infants have a raised mortality and morbidity it follows that in pemphigoid gestationis the fetal prognosis is impaired. In view of this it is essential that patients with pemphigoid gestationis are delivered in maternity units which have facilities for intensive care of the newborn.