The complement system in bullous pemphigoid. I. Complement and component levels in sera and blister fluids

C1q binding substances in pemphigus and bullous pemphigoid. Detection with a [131I] C1q binding assay

A modification of the [125I]C1q binding assay was developed to allow the estimation of C1q binding activity (C1q BA) in pemphigus and bullous pemphigoid sera. The modifications include lower final concentration of PEG 6000 (1-5%) which permitted the use of sera that had been stored at -20 degrees C for extended periods of time; use of 131I instead of 125I and an [131I] C1q concentration of 5 microng/ml rather than 1 microng/ml. EDTA was used at a final concentration of 0-13 M to obviate the need for heat inactivation of sera. Sera from seventy-one patients with pemphigus and from 142 patients with bullous pemphigoid were tested for C1q BA. Of these 40% of the pemphigus and 20% of the bullous pemphigoid patients showed elevated C1q BA. A relationship between elevated C1q BA in serum and active disease was noted. Sequential samples from forty patients with pemphigus and thirty-seven patients with bullous pemphigoid demonstrated two different types of relationship between serum antibody titres to cutaneous antigens and C1a BA. In some patients serum antibody titres and C1q BA increased and decreased simultaneously; in others, increase of C1q BA followed increase of antibody titre and coincided with its decrease. The latter relationship supports the hypothesis that C1q BA may represent at least in part antigen-antibody complexes containing cutaneous antigens.

Bullous pemphigoid in childhood: report of three cases and a review of literature

Three proven cases of bullous pemphigoid in childhood which responded to dapsone are reported. The clinical and immunological criteria for diagnosis were similar to those in the aged. This report emphasizes that the condition is a distinctive clinical entity and entirely different from dermatitis herpetiformis and benign chronic bullous dermatosis of childhood.

Herpes gestationis: fine structural pattern of immunoglobulin deposits in the skin in vivo

IgG and C3 deposits were observed in the basement membrane zone in a case with herpes gestationis. In addition, circulating IgG anti-basement membrane antibodies were found. Electron microscopic immunocytochemical investigations, performed with a peroxidase-antiperoxidase sandwich technique, revealed the in vivo-bound IgG to be localized at the epidermal basal lamina and to exhibit a distribution pattern which is identical to that reported for bullous pemphigoid.

Complement in pemphigus vulgaris and other bullous dermatoses

The behavior of the complement and of its components C4 and C3 has been studied in serum and in blister fluid both in patients with pemphigus vulgaris and other bullous dermatoses and in healthy subjects with experimentally induced blisters. The results are suggestive of local activation of the complement, in the blister fluid of patients with pemphigus vulgaris, pemphigus erythematosus and bullous pemphigoid according to the classical enzymatic sequence.

[The mechanism of antigen-antibody reaction at the basement membrane zone in bullous pemphigoid. The question of interaction of complement factors and bivalent cations (author's transl)]

1. In a medium poorly cationic indirect immunfluorescence of the basement membrane zone normally observed with preparations of sera from patients with pemphigoid has not be seen. 2. The fluorescence of basement membrane zone takes place if Fe2+ ions are added together with the antibasement zone antibodies. Evidently Fe2+ ions are essential for fixing antibodies. 3. With the method of indirect fluorescence the C3 component of complement could be observed after fixation of pemphigoid antibodies to the basement membrane zone. 4. EDTA prevents binding C3 too. Only after adding Fe2+ (not with Ca2+ or Mg2+) complement IF staining is demonstrable. Apparently EDTA causes the loss of fixing antibasement zone antibodies at first. Thereafter complement staining reaction is negative. 5. Participation of C1 could not be demonstrated using indirect IF staining. The alternate pathway to activation of C3 is discussed.

Immunologic phenomena in herpes gestationis

Immunofluorescence findings are of diagnostic significance in herpes gestationis. The studies in two cases demonstrated some complement components (chiefly C3 and C4, but no C(1q)), without immunoglobulins at the basement membrane zone and with no circulating anti BMZ antibodies. In one case IgG were found at the BM zone in one biopsy specimen, but were not demonstrable in several other biopsies. The IF findings seem to indicate both the alternate and classical pathways of complement activation, and speak in favor of a relation between herpes gestationis and bullous pemphigoid, in which sometimes the immunoglobulins are also not demonstrable and the immunofluorescent pattern is very much like that of herpes gestationis.

Complement activation in bullous skin diseases

Pemphigus, bullous pemphigoid, cicatricial pemphigoid, dermatitis herpetiformis, and herpes gestationis are members of the chronic vesiculobullous skin diseases of man. The complement system, including both the classical and alternative pathways, may be important in the pathogenesis of these diseases. In pemphigus, early complement components (C1, C4, and C2) appear to be activated in addition to later components (C3 and C5), suggestive of classical pathway activation. Participation of properdin in addition to early complement components suggests local activation of both complement pathways in bullous pemphigoid and cicatricial pemphigoid. Herpes gestationis and dermatitis herpetiformis may be bullous skin diseases entirely mediated by the alternate or properdin pathway. The specific immunopathologic findings in these diseases are discussed.

Diffuse normolipaemic plane xanthomatosis. An abnormal complement component profile

A patient with diffuse normolipaemic plane xanthomatosis, a benign monoclonal gammopathy, and a low total serum complement level is described. Functional haemolytic assays revealed decreased levels of C1, C4 and C2 components and elevated levels of the two terminal components C8 and C9. Radial immunodiffusion demonstrated low levels of C1q and C4 and a high level of C3. Both functional and immunochemical studies revealed extremely low levels of the inhibitor of C1 esterase. Anticomplementary activity was not present in the patient's serum. Despite low concentrations of the early reacting components of the classic complement pathway, the alternate pathway seemed to be intact. It was concluded that the patient had the recently delineated syndrome of acquired deficiency of the C1-esterase inhibitor.

Immunopathology of bullous pemphigoid. Basement membrane deposition of IgE, alternate pathway components and fibrin

Sixteen patients with bullous pemphigoid were examined using direct and indirect immunofluorescent techniques with antisera specific for C1q, C4, C3, C5, C3 proactivator, properdin, fibrinogen, IgA, IgM, IgG and IgE. The results of these studies are consistent with the activation of complement via the classical (antibody–C1q) sequence as well as via the alternate pathway. Fibrinogen and/or fibrin derivatives were demonstrated on the basement membrane of ten of fifteen patients tested and IgE basement membrane staining was found in four individuals.

Complement activation in pemphigus vulgaris blister fluid

Total haemolytic complement was reduced in blister fluids of four pemphigus vulgaris patients when compared to serum complement levels and other serum and blister fluid proteins. Complement levels in most control blister fluids, on the other hand, more closely approached their corresponding serum levels. Haemolytic C1, C4, C2, C3 and C5, measured in two pemphigus sera and blister fluids, were not measurable in one blister fluid and were extremely low in the second patient. C3 proactivator (C3PA) was absent from both of these blister fluids. Three of the blister fluids exhibited anti-complementary activity when tested with normal human serum. By adding one blister fluid to normal human serum, inhibition of haemolytic C1, C2, C3 and C5 with conversion of C3 and C3PA occurred. Activation of complement locally in pemphigus blister fluids would suggest a pathogenetic role for complement in this disease.

Evidence for complement activation via the alternate pathway in skin diseases, I. Herpes gestationis, systemic lupus erythematosus, and bullous pemphigoid

A patient with herpes gestationis, 6 of 6 patients with bullous pemphigoid, and 5 of 25 patients with systemic lupus erythematosus were found to have properdin deposited along the skin basement membrane.The patient with herpes gestationis demonstrated by immunofluorescence basement membrane deposition of C3 and C5 in the absence of C1q, immunoglobulins, and light chains. A second patient with herpes gestationis had C3 deposition with no demonstrable immunoglobulins or light chains. A thermolabile humoral factor(s) capable of depositing C3 (without C1q or C4) on normal skin basement membrane was found in the sera of both patients with herpes gestationis. No anti-basement membrane antibodies could be demonstrated in the sera of these patients.The patients with systemic lupus erythematosus and bullous pemphigoid who manifested properdin deposition also showed skin basement membrane deposits of C1q, C4, C3, C5, and immunoglobulins. C3 proactivator (C3PA) was also found deposited along the skin basement membrane of three patients with systemic lupus erythematosus and all six bullous pemphigoid patients. This study provides suggestive evidence that activation of complement is occurring via the alternate pathway in herpes gestationis. In systemic lupus erythematosus and bullous pemphigoid, both the classical (antibody) mediated activation of complement as well as the alternate pathway may be operative.