KF-1 monoclonal antibody defines a specific basement membrane antigen defect in dystrophic forms of epidermolysis bullosa

Epidermolysis bullosa: variability of expression of cicatricial pemphigoid, bullous pemphigoid, and epidermolysis bullosa acquisita antigens in clinically uninvolved skin

Indirect immunofluorescence was performed on skin from 13 patients with epidermolysis bullosa (EB) (simplex, 6; junctional, 2; dystrophic, 5) to compare the expression of 3 basement membrane components, bullous pemphigoid (BP) antigen, cicatricial pemphigoid (CP) antigen, and epidermolysis bullosa acquisita (EBA) antigen, in clinically uninvolved tissue. In addition, expression of laminin, type IV collagen, and KF-1 antigen was also evaluated. Whereas laminin, type IV collagen, and KF-1 antigen were each detectable in EB skin in a manner identical to that previously reported, marked variability was noted in the expression of BP, CP, and EBA antigens. However, no correlation was noted comparing lack of expression of any one of these latter antigens with either of the remaining two. Of these 3 antigens, BP antigen was the least often detectable, particularly in skin from patients with EB simplex. The lack of detectable BP antigen in EB simplex skin appeared to correlate with more extensive disease involvement and/or younger patient age. These findings may, therefore, limit the usefulness of BP serum in immunofluorescence mapping. Additionally, the disparity in expression of basement membrane antigens defined by BP and CP sera suggests that BP antigen and CP antigen are distinct entities.

The epidermal basement membrane zone--structure, ontogeny, and role in disease

Since many dermatologic diseases affect the epidermal basement membrane zone, there has been intense investigation into the role of epidermal basement membrane zone constituents in various skin diseases, particularly subepidermal blistering skin diseases. The epidermal basement membrane zone consists of four major structural components--the basal cell plasma membrane, the lamina lucida, the lamina densa, and the sublamina densa zone, which contains anchoring fibrils. The lamina lucida is composed of laminin, bullous pemphigoid antigen (a disease-specific glycoprotein identified by antibodies circulating in patients' sera), and other as yet poorly defined antigens identified by in vivo bound and circulating antibodies in the sera of patients with herpes gestationis, scarring pemphigoid, and others. The lamina densa consists of type IV collagen and KF-1 antigen, which is noncollagenous and is identified by a skin-specific monoclonal antibody. The sublamina densa zone consists of AF-1 and AF-2 antigens and the epidermolysis bullosa acquisita antigen(s). Knowledge of the structure and chemical composition of the basement membrane zone is critical to an understanding of some of the genetic and immunologically mediated blistering skin diseases.

The appearance of four basement membrane zone antigens in developing human fetal skin

In order to study the ontogeny of various structural and antigenic components of the basement membrane zone of human skin, we have examined skin specimens from 20 aborted fetuses ranging in gestational ages from 6 to 25 weeks, utilizing light microscopy, transmission electron microscopy, and indirect immunofluorescence with antibodies to bullous pemphigoid antigen, laminin, type IV collagen, and to the antigen defined by KF-1 monoclonal antibody. Both laminin and type IV collagen were detectable as early as 6 weeks of gestational age. In contrast, bullous pemphigoid antigen and the antigen defined by KF-1 antibody were not detectable before 10 weeks and 16 weeks, respectively. The appearance of bullous pemphigoid antigen correlated with stratification of the epidermis and the formation of hemidesmosomes and anchoring fibrils at the basement membrane zone. KF-1 antigen is first expressed when the epidermis is further stratified, hemidesmosomes and anchoring fibrils are present in greater numbers and with increased frequency at the dermal-epidermal junction, and hair follicles have begun to bud downward from the basal layer of the epidermis. Our findings suggest an orderly sequence to the appearance of these basement membrane zone components within human skin.

The use of monoclonal antibodies in skin basement membrane research

Recent experiments have indicated that it is possible to uncover new antigens within both the basement membrane zone and the epidermis of normal adult human skin by producing murine anti-human monoclonal antibodies following immunization with human skin preparations. Already one such monoclonal antibody has defined a biochemical defect that may be important in the pathogenesis of one of the more severe blistering skin diseases, dystrophic epidermolysis bullosa. It is likely that further attempts at hybridoma production using basement membrane extracts of skin will lead not only to the identification of other as yet unknown components of the human dermo-epidermal junction, but may also shed insight into the biochemical basis of one or more cutaneous diseases involving that region of the skin.