In vitro complement activation by antinuclear antibodies in the epidermis from patients with systemic sclerosis

Relevance of complement fixing antinuclear antibodies

BACKGROUND

Connective tissue diseases (CTDs) are a heterogeneous group of disorders defined by the association of a variety of clinical manifestations with immunologic and other laboratory findings. Overlap of syndromes and aberrant findings appear rather frequently.

METHODS

Sera of eight antinuclear antibody (ANA) negative, cases of subacute cutaneous lupus erythematosus (SCLE) with antibodies to Ro (SS-A) and a ninth case with clinical and laboratory signs of Sjögren's syndrome and systemic lupus erythematosus (SLE) were tested for complement (C') fixing antinuclear antibodies (C-ANAs). The ninth case was examined in depth by direct immunofluorescence (DIF) and a two-step "C + DIF" test of biopsies for C' fixation to in vivo bound ANAs, as well as serum tests for C-ANA, ANA, and SCLE markers.

RESULTS

Sera of five of the eight ANA negative, Ro(SS-A) positive SCLE cases had C-ANAs. The ninth case, a 50-year-old woman with clinical and laboratory signs of Sjögren's syndrome and SLE, gave a strong positive C + DIF reaction in the skin biopsy for in vivo bound ANAs that fix C', but negative ANAs and C-ANAs in routine serum tests; they revealed antimitochondrial antibodies. Serum tests on normal skin, however, revealed weak ANA and strong C-ANA reactions with in vitro fixed C'.

CONCLUSIONS

ANA negative cases of SCLE or Sjögren's syndrome may have C-ANAs. A case with Sjögren's syndrome and signs of SLE had both in vivo and in vitro C' fixing ANAs. C-ANA tests can aid in the identification of such cases.

Clinicopathological significance of cutaneous epidermal nuclear staining by direct immunofluorescence

Epidermal antinuclear antibody (ANA) staining was noted during routine direct immunofluorescence (DIF) of skin biopsies from 22 cases at St John's Dermatology Centre over a 2-year period. We have reviewed the clinical, serological and immunopathological features of these patients. They comprised 13 cases of lupus erythematosus (LE), 3 dermatomyositis, 1 morphoea, 1 systemic sclerosis, 1 CREST syndrome, 1 mixed connective tissue disorder and 1 probable cutaneous sarcoidosis. Five (38.4%) patients with LE had moderate to severe oral mucosal involvement. Epidermal nuclear staining (ENS) was seen following IgG deposition in 21 cases and IgA in only 1 case. Complement C3 staining was an additional feature in 1 patient. Circulating ANA was absent in 7 cases at the time of biopsy, confirming that this pattern of staining does not occur as a result of tissue contamination during processing. The presence of ENS by DIF corroborates a diagnosis of a connective tissue disorder, and our results suggest that it may also be associated with oral involvement in L.E.

Activation of the complement system in systemic sclerosis. Relationship to clinical severity

Using newly developed techniques, we investigated the complement pathways and the extent of their activation in patients with systemic sclerosis (SSc) of both the diffuse cutaneous and limited cutaneous types. Plasma levels of the fragments C3d, C4d, and Ba were measured in patients with SSc and in matched control subjects. All fragments and ratios were higher in SSc patients than in controls (P less than 0.05), demonstrating that complement activation occurs in SSc. Levels of C3d, C3d:C3, Ba, and Ba:factor B were higher in patients with diffuse cutaneous SSc patients than in controls (P less than 0.01). C3d, C3d:C3, C4d, and C4d:C4 levels were also higher in patients with limited cutaneous SSc than in controls (P less than 0.05). These results show that complement activation occurs in SSc patients and that it reflects clinical severity. Complement activation may therefore have a pathogenetic role in SSc, and its measurement may prove useful in monitoring the disease.