Studies in immunodermatology. VI. IF studies of autoantibodies to the stratum corneum and of in vivo fixed IgG in stratum corneum of psoriatic lesions.

Indirect immunofluorescent (IF) tests on sections of normal human skin reveal the presence of antibodies to the stratum corneum in most normal human sera. Sera absorbed with hyperkeratotic scales gave negative reactions. These reactions appeared to correspond to those of the stratum corneum antibodies which were first detected by Krough and Tonder by immune adherence, though this remains to be documented since the conjugate alone stained the stratum granulosum in a pattern comparable to that of the IF staining reported by Krough. The staining was caused by conjugates with high but not by those with low fluorescein to protein ratios. In indirect IF tests, comparable titers of stratum corneum antibodies were found in sera of psoriasis patients and control subjects. Since they reacted with the stratum corneum of the antibody producer they are referred to as autoantibodies. Direct IF tests of psoriatic lesions revealed the presence of in vivo bound IgG as well as other immunoglobulins and complement in the stratum corneum. To differentiate staining with conjugated protein from direct and indirect IF staining of the stratum corneum a four-compartment test was devised. Skin sections were treated with saline or with stratum corneum antibodies and then with conjugates without (compartments 1 or 2) or with (compartments 3 or 4) anti-IgG antibodies. Sections were read by the method of Kawamura and his associates with both UV and BV illumination. Compartment 3 is a direct IF test and compartment 4 is an indirect IF test. In four-compartment tests performed on both biopsies of psoriatic lesions or scales the difference between compartments 1 or 2 and 3 affords a measure of in vivo bound IgG and the difference between compartments 3 and 4 provides information on the presence of free stratum corneum antigen. With this four-compartment test system it was found that in vivo fixation of IgG occurs in the intercellular areas of the stratum corneum of psoriatic lesions or scales and that this corresponds to the site of binding of the stratum corneum autoantibodies. This in vivo binding of IgG in the stratum corneum of psoriatic lesions resembles somewhat the intercellular fixation of IgG in the stratum spinosum in pemphigus. In the materials examined in these preliminary studies most, if not all of the stratum corneum antigen appeared to be covered with in vivo bound IgG.