Immunofluorescence patterns in sun-exposed and not-sun-exposed skin of healthy individuals

Immunofluorescence studies were performed on the sun-exposed (S) and not-sun-exposed (N) skin of 25 healthy volunteers regarding the incidence of the five Ig classes, albumin, fibrinogen, C1q, C4, C3B, C3c, C3d, C5, C3PA and properdin. In addition a comparative study of two so-called anti-complement antisera was made, one (CI) containing anti-(C4+C3a+C3d), the other (CII) anti-(C3B+C3c). In all biopsies the epidermal basement membrane (BM) was stained positively with anti-C3d in a fibrillar, interrupted linear, or granular pattern. A band-like picture of the BM was observed with anti-IgG , anti-albumin and anti-fibrinogen in three biopsies of the S skin. In two other S skin biopsies a lichenoid pattern was found with anti-fibrinogen, anti-C3d and IgM. The latter antiserum caused a weakly positive band-like picture of the BM, occasionally together with granular deposits, more often in the S skin (11) than in the N skin (4). In the capillary walls, granular deposits of IgM, C3d and occasionally C3c were seen in both the S skin (7) and the N skin (13). In the subjacent vessels, globular deposits positive with anti-C3d, C5 and C3c were found predominantly in the S skin. In the M. arrector pili, granular deposits of C3d and, less obviously, C5, properdin and IgM were frequently observed. A band-like, linear, or granular picture of the BM of the adnexal structures was caused by anti-C3d. IgG was found around the sweat gland in about 30%, but the other serum proteins were only rarely present. The IF patterns of the two so-called anti-complement sera showed marked differences, which were apparently caused by the presence of anti-C3d in the CI serum. The significance of these findings for the diagnostic and pathogenetic interpretation of IF results in pathology are outlined briefly.