The pilosebaceous duct is one area of the skin where, surprisingly, monoclonal antibodies have not been extensively used. The reason for this is twofold: firstly, few biologists are investigating acne and, secondly, careful serial sectioning is necessary.

Clearly there is considerable scope for the use of monoclonal antibodies at this site; such techniques could yield useful information on intra- and intercellular structures and possibly their control..

Using monodansylcadaverine as a fluorescent, lysine substrate analogue, De Young et al measured alterations in the histochemical profile of epidermal transglutaminases during human and coal tar induced rabbit ear comedogenesis.12 When compared to the normal pilosebaceous follicles of both species, a marked increase in enzyme specific fluorescence was seen in the hyperplastic epidermal lining and in the epithelium of the sebaceous duct in human and rabbit early lesions.

In mature human open and closed comedones an intact band of epidermal transglutaminase activity corresponding to the differentiating epidermal cell layers was seen to surround the lesion. In most lesions, epidermal transglutaminase activity was closely opposed to the plasma membrane of the differentiating keratinocytes, the site of cornified envelope formation.

In normal human and rabbit interfollicular epidermis the cornified layer immediately above the fluorescent granular layer was histochemically inactive, while the surface stratum corneum showed an increase in activity. A similar phenomenon was observed in comedones. The pattern of activity may relate to the process of desquamation.

These authors suggest that the changes in transglutaminase activity observed during comedogenesis may indicate the possibility that inhibitors of epidermal transglutaminase could be useful in acne therapy..

A monoclonal antibody, using envelopes from cultured epidermal cells as immunogen which specifically recognizes a particular class of epidermal cell envelope, has recently been developed. From immunoblotting and immunolocalization studies, the anti-envelope monoclonal specifically recognizes an antigenic determinant on the cross-linked envelope structure but not on cross-linked envelope components, such as involucrin or plasma membrane proteins.

In indirect immunotluorescent studies on sections of normal human epidermis, the monoclonal recognizes only the cell envelopes produced in the upper regions of the intrafollicular areas. In normal epidermis, a relatively sharp boundary exists between the positive intra- and the negative interlollicular regions.

Some noninflamed, whitehead acne lesions have an increased thickness of intrafollicular epidermis possessing cell envelopes concomitant with the epidermal hyperplasia observed in these lesions..

In addition, the interfollicular epidermis neighbouring the involved hair follicle now also demonstrates positive staining extending out to a variable distance away from the actual acne lesion . This acquisition of antibody positivity in the normally negative interfollicular epidermis bears considerable resemblance to the development of positivity in the interfollicular epidermis of psoriatic lesions and normal epidermis placed into organ or tissue cultures..

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