Hematoxylin stainable epidermal protein of the newborn rat. IV. The change of antigenicity in situ by transglutaminase as determined by an immunofluorescent study.

Based on the activity of transglutaminase, the change of antigenicity in situ of hematoxylin stainable protein (HSP) purified from 3-day-old rat epidermis and located on the cell membrane region of the stratum corneum was investigated by indirect immunofluorescent technique using a polyclonal antibody against hematoxylin stainable protein. Three different techniques were employed: (i) the skin section was incubated with a commercial guinea pig liver transglutaminase (GLT), (ii) the skin section was incubated with an epidermal extract of Tris-HCl (EX), and (iii) the skin section was incubated with an epidermal extract of 1% Triton X-100 (EXT). The sections incubated in Tris-HCl or Triton X-100 were used as controls. Each incubation was done both in the presence and absence of Ca2+ ions. After these incubations, an indirect immunofluorescent technique using a polyclonal antibody was performed. In the presence of Ca2+ ions, the specific fluorescence of the cell membrane region of the entire stratum corneum cells disappeared after the preincubation with GLT. That of the lower one third of the stratum corneum disappeared after the incubation with EXT. In contrast, in the absence of Ca2+ ions, no preincubation with GLT, EX, or EXT showed any disappearance of the fluorescence anywhere in the stratum corneum. There was also no disappearance of the fluorescence in the control sections. These findings suggest that the antigenicity of HSP in situ could be lost by the activity of transglutaminase.