A simple technique for immunoelectronmicroscopic localization of Ig on tissue sections with special reference to cutaneous pathology

Demonstration of intra- and extracellular localization of bullous pemphigoid antigen using cryofixation and freeze substitution for postembedding immunoelectron microscopy

Using low-temperature postembedding techniques for immunoelectron microscopy, we succeeded in demonstrating the precise localization of bullous pemphigoid antigen (BP-Ag) in normal human skin. Small pieces (less than 1 mm3) of normal adult skin were rapidly frozen in liquid propane at -190 degrees C and subjected to freeze substitution with 100% methanol at -80 degrees C. Specimens were embedded in Lowicryl K11M at -60 degrees C which was polymerized under ultraviolet radiation at -60 degrees C. Ultrathin sections were incubated with BP sera followed by rabbit anti-human IgG and colloidal-gold conjugated anti-rabbit IgG. Epidermal ultrastructure was generally well preserved: the basal cell plasma membrane and intra- and extracellular components of hemidesmosomes could be resolved. Gold particles were mainly distributed on and around the hemidesmosomes in both intra- and extracellular sites, with most of the labelling being inside the basal keratinocytes and within about 300 nm of the basal plasma membrane. No specific labelling was observed beneath melanocytes or when normal human serum was used as a control instead of BP serum. Our observations indicate that BP-Ag is localized in and around hemidesmosomes in normal human skin and that the antigen has both intracellular and extracellular domains with the major component occurring inside the cells.

The use of chemically split tissue in the detection of circulating anti-basement membrane zone antibodies in bullous pemphigoid and cicatricial pemphigoid

Human skin and mucous membranes were used to detect circulating auto-antibodies by indirect immunofluorescence in 20 patients with bullous pemphigoid and eight with cicatricial pemphigoid. The tissue substrate was used intact and after chemical separation through the basement membrane zone (BMZ) by incubation with I M NaCl. Chemically split skin and oral mucosa provided a more sensitive assay for demonstrating circulating anti BMZ antibodies. Use of a battery of substrates increased the number of positives in bullous pemphigoid from 30% detected on monkey oesophagus to 100% (tissue battery). In cicatricial pemphigoid there was an increase in the proportion of positive sera from 13% (monkey oesophagus) to 88% (tissue battery). In addition, a different class of antibody was frequently detected on split tissue substrate suggesting that new antigens are exposed by this procedure.

Immunoelectron microscopic identification of human NK cells by FITC-conjugated anti-Leu-11a and biotinylated anti-Leu-7 antibodies

Human natural killer (NK) cells have been reported to express various surface antigens. The majority and the most functionally potent NK cells are Leu-11a (NKP-15) positive cells. Only a small number of functional NK cells express Leu-7 (HNK-1) antigen. In the present study, we have established techniques for immunoelectron microscopic identification of NK cells by mouse monoclonal FITC-conjugated anti-Leu-11a and biotinylated anti-Leu-7 antibodies. Ficoll-Hypaque-isolated peripheral blood lymphocytes (PBL) were reacted with the specific antibodies before or after fixation in a 1% glutaraldehyde/1% paraformaldehyde fixative. Prefixation labeling of viable cells with the antibodies was carried out at 4 degrees C or 37 degrees C. Cells prelabeled with anti-Leu-11a antibody were reacted with secondary antibodies either before or after fixation. Anti-Leu-7 antibody was stained directly via an avidin-biotin-peroxidase (ABC) system, anti-Leu-11a antibody was stained indirectly by the ABC immunoperoxidase procedure via a biotinylated anti-mouse IgG secondary antibody or by a 10 nm or 40 nm colloidal gold-labeled anti-mouse IgG antibody. Results indicate that Leu-7 antigen could be localized by incubation with the specific antibody either before or after 20 min fixation; however, Leu-11a antigen was totally abrogated following the same fixation procedure. The Leu-11a antigen was well stained by the methods of prefixation labeling of cells with anti-Leu-11a antibody and incubation with a biotinylated secondary antibody and the ABC system after fixation. With respect to colloidal gold labeling, better results were obtained when cells were reacted with the gold-labeled antibodies immediately after incubation with anti-Leu-11a antibody but before fixation. Ultrastructurally both Leu-7 positive (+) and Leu-11a positive (+) cells shared common ultrastructural features associated with large granular lymphocytes. Using the above described techniques, we found approximately 2-5% Leu-7+ and 9-15% Leu-11a+ cells in the PBL of healthy donors. The overall results suggest that Leu-11a antigen is more sensitive to glutaraldehyde/paraformaldehyde fixation than Leu-7, since it can be localized only by prefixation labeling procedures; the ABC immunoperoxidase procedure is an ideal technique for labeling NK cells for light and electron microscopic enumeration; the immunogold method provides an adequate technique for labeling NK cells which are designated for ultracytochemical studies.

Bullous pemphigoid antigen localization suggests an intracellular association with hemidesmosomes

Autoantibodies to a normal component of stratified squamous epithelia, the bullous pemphigoid antigen (BPA), are synthesized in patients with the disease bullous pemphigoid. We have used these sera to study the distribution of BPA in vivo and in vitro. At low magnification, indirect immunofluorescent staining for BPA is linear at the basement membrane zone (BMZ) of skin and many other epithelial tissues. At higher magnification however, we observed a punctate staining pattern for BPA which was regular in appearance and suggested localization of BPA to discrete structures at the BMZ. Subsequent immunoelectron microscopy using both peroxidase and colloidal gold labeling techniques with patients' sera or IgG, revealed that BPA is associated with hemidesmosomes--putative adhesion structures at the BMZ, based on their similarity in ultrastructure to desmosomes. More specifically BPA was immunolocalized to the cytoplasmic face of hemidesmosomes and was not observed extracellularly in the basement membrane. In stratifying and nonstratifying cultures of rat keratinocytes, BPA is expressed intracellularly and not in the cell-derived matrix, unlike other known basement membrane components. These cells also synthesize BPA in vitro, and immunoprecipitation from metabolically labeled cultures revealed a 220 kD polypeptide under reducing conditions. From these observations we conclude (1) that BPA is a 220 kD polypeptide component either of or associated with hemidesmosomes, and (2) that it is localized intracellularly both in vivo and in vitro. We suggest that BPA is not normally a lamina lucida component, but that it may form part of a linkage between the cytoskeleton and the basement membrane.

Immunoelectron microscopic studies in IgA linear dermatosis

The authors investigated three cases of IgA linear dermatosis by immunoelectron microscopy. In two of the cases there were additionally some IgG deposits in the basement membrane zone. The arrangement of the IgA deposits was found to vary. In two cases it was of the dermal and the lamina lucida type at the same time, and in one case it was so close to basal cell membranes as to leave an electronlucent space on the side facing the basal lamina. In the third case, the arrangement (only IgG and complement were studied) was exclusively of the dermal type. In one of the cases the deposits had first, i.e., 1 1/2 years earlier, been confined to the lamina lucida, whereas now they were also seen below the basal lamina, although the clinical condition of the patient had remained unchanged. It would seem that the localization of IgA deposits in the basement membrane zone may vary, depending on the evolution of the disease.

Ultrastructural demonstration of T cells in cutaneous tissue sections using specific anti-human T cell antiserum

The presence of T lymphocytes in the situ in cutaneous infiltrates of contact dermatitis and lichen planus has been demonstrated by an immunoelectronmicroscope technique. A specific anti-human T cell antiserum labelled with peroxidase-conjugated anti-immunoglobulin serum was used to reveal the specific human T lymphocyte antigen (HTLA) which was visualized ultrastructurally. This technique shows that labelling is limited to the surface membrane and allows study of the in situ interrelationship of T cells.