Complement Indirect Immunofluorescence Research Articles

Immunoblot analysis of IgG subclasses of circulating antibodies in bullous pemphigoid

Sera from 20 patients with bullous pemphigoid (BP) were analyzed for the subclass distribution of IgG autoantibodies by Western immunoblotting of normal human heat-separated epidermal extracts. Strips were sequentially probed with patient sera, monoclonal antibodies (Mab) anti-human IgG 1–4, and a labeled anti-mouse Ig. The relative dilutions of each subclass-specific Mab were determined in dot immunobinding experiments in order to give uniform reactivity to the corresponding human IgG subclass. Circulating BP autoantibodies reacting with the major BP antigen of 220 kDa and/or a 165-kDa band showed a stricking predominance of IgG 4. Overall, IgG 4 was the major subclass reactive with the 220-kDa band, whereas, in addition to IgG 4, IgG 1 and IgG 2 were frequently represented in the response to the 165-kDa band. Complement fixation of circulating BP antibodies was studied by complement indirect immunofluorescence using human serum as source of complement and FITC goat anti-human C3, C1q, and C4, on normal human skin substrate. When circulating BP antibodies contained IgG 1 or IgG 2 in addition to IgG 4, they fixed C3 and, in some cases, C1q and C4, suggesting complement activation by either the classical or the alternate pathway.

Autoimmunity in psoriasis

Immunofluorescence (IF) studies using the test providing information on the reactivity of stratum corneum (SC) antibodies and their in vivo binding have been performed in 193 cases of psoriasis and 89 cases with other dermatoses. It has been shown that: 1. Essentially all fully developed, active psoriatic lesions had IgG deposits in the stratum corneum at the sites of the SC antigen, presumably due to in vivo binding of SC antibodies. 2. In various forms of psoriasis SC antigen sites appeared to be completely or almost completely satured with in vivo deposits of IgG as seen in tests with SC antibodies. 3. In most but not all lesions complement components C3 and/or C4 was found in a comparable pattern in the SC, especially when multiple specimens of single cases were studied. Partial or complete saturation of the SC antigen could be observed by the performance of complement indirect IF tests for SC antibodies in such specimens. 4. In lesions with typical histology of psoriasis the above-mentioned immunologic characteristics appeared to be a constant finding. However, in specimens of recent lesions which had not yet developed typical histology a proportion (2 of 17) were negative both for IgG and complement deposits. In receding lesions weak deposits of IgG were present only in a few specimens and complement deposits were as a rule negative. 5. In a group of 89 control specimens of other dermatoses only occasional cases gave the psoriasiform IF pattern, but about 30% of the specimens gave positive reactions in the SC though these were usually of a different pattern.