Increased expression of complement C3c, iC3b, and cells containing CD11b or CD14 in experimentally induced psoriatic lesion

Psoriasis is a chronic inflammatory skin disease with a characteristic isomorphic reaction, i.e. the Kobner reaction, induced by slight epidermal trauma. In this study, the tape-stripping technique was used to induce the development of Kobner reaction in 18 subjects with psoriasis. Eight subjects developed a positive reaction. To study the early cellular changes, skin biopsies were taken at the baseline and subsequent time points of 2 h, 1 d, 3 d, and 7 d for the immunostaining of complement C3c, iC3b, and cells expressing complement receptor 3 (CD11b/CD18; a receptor of iC3b) or CD14. The results show that the positive Kobner reaction is associated with rapid (2 h-1 d) and sustained (3-7 d) increase in the expression of epidermal C3c and iC3b and dermal C3c. In addition, there was a positive correlation between CD11b+ and CD14+ cells in baseline and 2 h-1 d biopsies with a subsequent increase in CD11b+ and CD14+ cells in 3-7 d biopsies in the Kobner-positive group. In the Kobner-negative group, only a transient increase in epidermal iC3b at 2 h-1 d, as well as rapid (2 h-1 d) and sustained increase (3-7 d) in dermal iC3b and CD14+ cells, was observed. In experiments with cultured monolayer keratinocytes, a slight cell damage already at 30 mJ/cm2 ultraviolet B irradiation led to increased expression of C3c, but not iC3b. Therefore, there are marked differences between Kobner groups in respect to the expression of C3c, iC3b, and cells expressing CD11b or CD14. Of note is the rapid and sustained increase in epidermal C3c and iC3b in the positive Kobner reaction. The isomorphic psoriatic reaction is especially associated with rapid and sustained increase in the expression of epidermal C3c and iC3b and dermal C3c. In addition, the significant correlation between CD11b+ and CD14+ cells in 0 d and 2 h-1 d biopsies, as well as the subsequent increase in CD11b+ and CD14+ cells in 3-7 d biopsies, in the Kobner-positive group suggests that there are differences between Kobner groups in respect to dermal cellular environment already before the induction of the isomorphic psoriatic reaction. The expression of C3c immunoreactivity in cryosections from a representative Kobner-positive patient with psoriasis on day 0 (a), day 1 (b), and day 7 (c).The immunohistochemical staining of CD11b+ cells in cryosections from a Kobner-positive patient with psoriasis on day 0 (d) and day 7 (e). Graphical Abstract