Ultrastructural basis for antigen mapping using sodium chloride-separated skin.

In many cases of autoimmune blistering skin diseases indirect immunofluorescence with serum of patients on 1 M NaCl-separated skin represents a rapid diagnostic tool before the use of more complicated immunoelectron microscopy. The present study demonstrates that in skin samples from five adults, separated using 1 M NaCl, 0.15 M NaCl and 0.01 M phosphate buffered saline (PBS), the split formed within the lamina lucida at an identical ultrastructural level. The sub-basal dense plate (SDP) with a wreath of anchoring filaments remained on the epidermal side of the split adjacent to the hemidesmosomal part of the plasma membrane of basal keratinocytes. The base of the split blister was constituted from the lamina densa, with a remote possibility of some anchoring filaments attached. We demonstrate that antigens on the roof of the NaCl- or PBS-split blister may be associated, beside intracellular hemidesmosomal structures, with the SDP and basement membrane components between the SDP and the basal keratinocytes as well as with anchoring filaments attached to the SDP. The observations reported here allow a more precise mapping of antigen determinants in blistering skin diseases.