Electron microscopic and immunocytochemical studies of the sequence of events in psoriatic plaque formation following tape-stripping.

Electron microscopic and immunocytochemical studies were performed on sequential biopsies following the tape-stripping of the uninvolved skin in 12 patients with psoriasis. In the biopsies taken after 5 min for up to 7 days during the pre-psoriatic phase, there were initial lymphocyte-Langerhans cell interactions as well as interactions between lymphocytes and keratinocytes. In biopsies taken after 6-8 weeks during the proliferative phase there were lymphocyte-macrophage interactions. In the 24-h and 7-day biopsies there were close contacts between epidermal lymphocytes and keratinocytes via microvilli, with blebbing of the keratinocyte plasma membranes and granular cytoplasmic changes around these microvilli. Few basal keratinocyte herniations were noted during this phase. The 6-8-week biopsies of Köbner-positive patients were characterized by a marked increase in lymphocyte-macrophage interactions via similar microvillous processes with associated electronlucent areas suggestive of cytotoxicity.