Decreased Expression of Epidermal Cytoplasmic Antigens in Cultured Human Keratinocytes

The expression of upper cytoplasmic (U-CYT) antigens which are expressed only in the superficial layers of the epidermis and are markers of epidermal cell differentiation in vivo and of basement zone (BMZ) antigens reacting with bullous pemphigoid serum was studied in keratinocytes in tissue culture. The cells were cultured at an acid pH (5.6–5.8) similar to that of skin and without feeder cells, dermal tissue, or collagen. It was found that the expression of U-CYT antigens decreased markedly in culture. These antigens were expressed in 45–65% of epidermal cells prepared from fresh skin, but in only 5–10% of cells which had been grown in primary culture over 1 mo, and in no cells in secondary or tertiary culture. By contrast, BMZ antigens continued to be expressed in culture. These antigens were expressed by 20–35% of epidermal cells prepared from fresh tissue and by 15–35% of keratinocytes in primary, secondary or tertiary culture. These findings indicate that U-CYT and BMZ antigens can be used to type subpopulations of human keratinocytes in suspension, and suggest that the differentiation of these cells in vitro differs from that which occurs in vivo

Expression of Vitiligo Antigen on a Revertant Line of Hamster Melanoma Cells

Our laboratory has recently reported that over 80% of patients with common vitiligo have circulating antibodies to cell-surfacer antigens on normal human melanocytes. The slow growth rate of these cells limits the assays that can be performed for antibody detection. We now have found that the antigens defined by vitiligo sera on melanocytes are also expressed on FF cells, a revertant line of hamster melanoma cells. These antigens can be detected both by indirect immunofluorescence and specific immunoprecipitation assays. The presence of “vitiligo” antigens on hamster FF cells will aid further study of the abnormal immune response in vitiligo

BINDING OF ANTIGEN BY IMMUNOCYTES : I. EFFECT OF LIGAND VALENCE ON BINDING AFFINITY OF MOPC 315 CELLS FOR DNP CONJUGATES

The binding of antigen to cells with antibody on their surface has been studied in a model system consisting of murine myeloma cells (MOPC 315) and DNP conjugates. Specific binding occurred between the DNP groups of DNP conjugates and cell surface immunoglobulin. Using this model, the binding affinities of multivalent and univalent DNP conjugates were measured directly by equilibrium-binding techniques and indirectly by displacement of bound conjugate with univalent hapten. With both approaches the multivalent conjugate was shown to bind to cells with an avidity 100–300 fold greater than the univalent hapten. Nonspecific binding of unrelated protein and repeated washing of cells was found to markedly dedecrease the specific binding of univalent conjugates, presumably because the relatively weak bonds dissociate readily

Autoantibodies to Hair Follicles in C3H/HeJ Mice With Alopecia Areata–Like Hair Loss

We have previously described spontaneous but reversible hair loss that clinically and histologically resembles human alopecia areata in a colony of C3H/HeJ mice. Alopecia areata in humans is associated with antibodies to hair follicles. This study was conducted to determine whether C3H/HeJ mice with hair loss have a similar abnormal antibody response to hair follicles. Eighteen C3H/HeJ mice with alopecia, 12 unaffected littermates, and 15 control mice were examined for circulating antibodies to C3H/HeJ anagen hair follicles by indirect immunofluorescence and against extracts of isolated C3H/HeJ and human anagen hair follicles by immunoblotting. Using both procedures, antibodies to anagen hair follicles were present in all C3H/HeJ mice with alopecia but in none of the control mice. The antibodies were also present in some unaffected C3H/HeJ littermates but were absent in mice of an unrelated strain with inflammatory skin disease and alopecia, indicating that their appearance did not result from the hair loss. These antibodies reacted to hair follicle–specific antigens of 40–60kDa present in murine and human anagen hair follicles. These antigens were also reactive with human alopecia areata antibodies. Some of the antibodies in both C3H/HeJ mice and humans with alopecia areata reacted to antigens of 44 and 46 kDa, which were identified as hair follicle–specific keratins. This study indicates that C3H/HeJ mice with hair loss have circulating antibodies to hair follicles similar to those present in humans with alopecia areata. These findings confirm that these mice are an appropriate model for human alopecia areata and support the hypothesis that alopecia areata results from an abnormal autoimmune response to hair follicles

Reliability and Convergent Validity of Two Outcome Instruments for Pemphigus

A major obstacle in performing multicenter controlled trials for pemphigus is the lack of a validated disease activity scoring system. Here we assess the reliability and convergent validity of the PDAI (pemphigus disease area index). A group of 10 dermatologists scored 15 patients with pemphigus to estimate the inter- and intra-rater reliability of the PDAI and the recently described ABSIS (autoimmune bullous skin disorder intensity score) instrument. To assess convergent validity, these tools were also correlated with the Physician’s Global Assessment (PGA). Reliability studies demonstrated an intra-class correlation coefficient (ICC) for inter-rater reliability of 0.76 [95% CI = 0.61–0.91] for the PDAI and 0.77 [0.63–0.91] for the ABSIS. The tools differed most in reliability of assessing skin activity, with an ICC of 0.39 [0.17–0.60] for the ABSIS and 0.86 [0.76–0.95] for the PDAI. Intra-rater test-retest reliability demonstrated an ICC of 0.98 [0.96–1.0] for the PDAI and 0.80 [0.65–0.96] for the ABSIS. The PDAI also correlated more closely with the PGA. We conclude that the PDAI is more reproducible and correlates better with physician impression of extent. Subset analysis suggests that for this population of mild to moderate disease activity, the PDAI captures more variability in cutaneous disease than the ABSIS