Stephen I. Katz

Defective lymphoid development in mice lacking expression of the common cytokine receptor γ chain

The common gamma chain (gamma c) of the IL-2, IL-4, IL-7, IL-9, and IL-15 receptors is defective in humans with XSCID. Mice lacking gamma c expression had hypoplastic thymuses; the thymocytes responded to gamma c-independent mitogens, but not gamma c-dependent stimuli. Splenic T cells were diminished at 3 weeks of age, but CD4+ T cells markedly increased by 4 weeks. B cells were greatly diminished in contrast with the situation in XSCID. NK cells, gamma delta intestinal intraepithelial lymphocytes, dendritic epidermal T cells, peripheral lymph nodes, and gut-associated lymphoid tissue were absent. These findings underscore the importance of gamma c in lymphoid development. Moreover, differences in humans and mice lacking gamma c expression indicate species-specific differences in the roles of gamma c-dependent cytokines or in the existence of redundant pathways. These mice provide an important model for studying the pathophysiology provide an important model for studying the pathophysiology of and gene therapy for human XSCID.

Epidermal Langerhans cells are derived from cells originating in bone marrow

Langerhans cells constitute a morphologically well characterised subpopulation (3–8%) of mammalian epidermal cells which, in contrast to the bulk of epidermal cells, bear Fc-IgG and C3 receptors1, express immune response-associated (Ia) antigens and function as antigen-presenting cells and allogeneic stimulatory cells to primed T lymphocytes2–5. The ontogeny of Langerhans cells has been a subject of considerable debate since their discovery6. Although some studies suggest that Langerhans cells are of mesenchymal as opposed to neural or melanocytic origin7, direct evidence for this has not been presented. In this study we demonstrate that, after 3 weeks, most of the Langerhans cells (LC) in parental skin which had been transplanted on to F1 hybrids were of recipient origin whereas keratinocytes remained of donor origin; this indicates that the LC are derived from a mobile pool of cells. Furthermore, in studies of skin from radiation-induced bone marrow chimaeric animals we found that, depending on the strain combination, up to 80% of the epidermal LC were derived from the bone marrow of the donor animals.

Characterization of bullous pemphigoid antigen: A unique basement membrane protein of stratified squamous epithelia

Abstract Bullous pemphigoid (BP) antigen is a normal basement membrane zone antigen of epidermis and other stratified squamous epithelia. It is defined immunologically by antibodies in the sera of patients with the subepidermal blistering disease BP. In this study we sought to demonstrate that epidermal cells synthesize this antigen, to determine the immunological specificity of BP antibodies and to characterize this antigen. Cultured human epidermal cells (HEC) and a spontaneously transformed mouse epidermal cell line (Pam) both demonstrated BP antigen by indirect immunofluorescence. To characterize the antigen, these cells were radiolabeled with 35 S-methionine or 14 C-amino acids and extracts were immunoprecipitated using nine different BP sera. Immunoprecipitated proteins were identified using sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. All nine BP sera precipitated a protein with disulfide-linked chains of apparent molecular weight approximately 220 kd. Eight normal human sera and six pemphigus vulgaris sera, as well as antibodies directed against fibronectin and laminin, did not precipitate this protein. Furthermore, it was not precipitated by BP sera from radiolabeled extracts of fibroblasts. The protein was soluble in Tris-HCI buffered saline but was not secreted into the culture medium. These studies demonstrate that BP antigen is synthesized by epidermal cells in culture, different patients with BP have antibodies against the same protein, and BP antigen can be identified on SDS-PAGE as a high molecular weight protein consisting of disulfide-linked chains of approximate molecular weight 220 kd.

Origin and Function of Epidermal Langerhans Cells

In 1868, the medical student Paul Langerhans discovered a population of dendritic cells in the suprabasal regions of the epidermis by impregnating human skin with gold salts (Langerhans 1868). These cells are now eponymously referred to as Langerhans cells (LC). Since the gold chloride stain has a particular affinity for nerve tissue, Langerhans considered these cells to be a part of the nervous system. This theory was maintained by other investigators until the 196Os {Ferreira-Marques 1951, Niebauer & Sekido 1965). Throughout the 195Os and 196Os, another hypothetical concept had evolved which postulated a relationship between LC and melanocytes. According to that theory, LC were regarded either as worn-out melanocytes (Masson 1951), as daughter cells of dividing melanocytes (Zelickson 1966), or as melanocytes in an arrested stage of development (Breathnach 1963). Although the electron microscopic studies of Birbeck et al. (1961) had revealed that LC contained unique cytoplasmic organelles, these authors also favored the view of LC being derived from melanocytes. This postulated ontogenic relationship between LC and melanocytes and the suggestion that LC were a component of nervous tissue were disproven by grafting experiments of Breathnach et al. (1968). These authors transplanted limb buds of l()-day-old mouse embryos which had been deprived of their neural crest components into the spleens of histocompatible animals where they continued to grow and to differentiate. LC were regularly found in epidermis and in subepidermal connective tissue from skin differentiated from the neural

Antibodies to Type II Collagen in Relapsing Polychondritis

Relapsing polychondritis is a disorder of unknown cause characterized by the destruction of cartilage. To test the hypothesis that immunologic mechanisms are involved in the pathogenesis of relapsing polychondritis, we analyzed the serum of 15 patients for the presence of antibodies to cartilage. Antibodies to Type II (cartilage) collagen were found in the serum of five patients at the time of acute symptoms. No antibodies were detected either to cartilage proteoglycan or to other collagen types. The antibodies were detected at the onset of the disease and their titers appeared to correlate with severity of disease. Circulating immune complexes were also detected in the serum of these patients. Our findings support an immunologic involvement in this condition.

Defective Fc-Receptor Functions Associated with the HLA-B8/DRw3 Haplotype: Studies in Patients with Dermatitis Herpetiformis and Normal Subjects

Dermatitis herpetiformis is associated with the HLA-B8/DRw3 haplotype in over 90 per cent of patients, and various percentages have been reported to have circulating immune complexes. Since removal of immune complexes from the circulation is thought to depend on the Fc-receptor function of tissue macrophages, we studied this function by measuring the clearance of IgG-sensitized autologous erythrocytes in 16 patients with dermatitis herpetiformis, in normal controls with the HLA-B8/DRw3 haplotype, and in randomly selected controls. All patients were HLA-B8 positive, and all of 12 patients tested were HLA-DRw3 positive. Erythrocyte clearance was reduced in eight of the 16 patients, but did not correlate with immune-complex levels. Four of eight controls with HLA-B8/DRw3 also had delayed Fc-receptor-mediated clearance as compared with normal controls. In addition, both patients and HLA-B8/DRw3-positive controls had decreased percentages and total numbers of T cells bearing Fc receptors for IgG. These findings indicate a functional Fc-receptor defect associated with the HLA-B8/DRw3 antigens.

Productive infection of dendritic cells by HIV-1 and their ability to capture virus are mediated through separate pathways.

There is substantial evidence that dendritic cells (DC) residing within epithelial surfaces (e.g., Langerhans cells) are the initial cells infected with HIV after mucosal exposure to virus. To study DC-HIV interactions in detail, we propagated Langerhans cell-like DC from cord blood CD34(+) cells and from adult blood plastic-adherent PBMC in the presence of cytokines (GM-CSF, IL-4, and/or TNF-alpha). DC pulsed overnight with HIVBaL or HIVIIIB were infected productively with both viral subtypes (as assessed by PCR, supernatant p24 protein levels, electron microscopy, and antibody staining). Productive infection could be blocked by anti-CD4 mAbs, RANTES (regulated upon activation, normal T cell expressed and secreted) (for HIVBaL), stromal cell-derived factor-1 (for HIVIIIB), or azidothymidine added during the HIV pulse, as well as by blocking DC proliferation. However, pulsing DC with HIV under these blocking conditions had no effect on the ability of DC to capture virus and transmit infection to cocultured antigen-stimulated CD4(+) T cells. Thus, we show by several criteria that (a) productive infection of DC and (b) the ability of DC to capture virus are mediated through separate pathways. We suggest that strategies designed to block mucosal transmission of HIV should consider interfering with both virus infection and virus capture by DC.

Pemphigus Antibodies Identify a Cell Surface Glycoprotein Synthesized by Human and Mouse Keratinocytes

Pemphigus is an antibody-mediated autoimmune skin disease in which loss of cell-to-cell contacts in the epidermis results in blister formation. Patients with pemphigus develop antibodies that bind to the keratinocyte cell surface, the site of primary pathology. The purpose of this study was to characterize the antigen(s) to which pemphigus antibodies bind. Because we could detect pemphigus antigen by indirect immunofluorescence on the surface of multiply-passaged cells in cultures of both a spontaneously transformed mouse keratinocyte cell line (Pam) and normal human epidermal cells, we used these cells as a source of antigen. In order to demonstrate biosynthesis of antigen and to characterize the antigen(s), we radiolabeled cell cultures with [(14)C]glucosamine or d-[2-(3)H]mannose and used different pemphigus sera to immunoprecipitate antigen from nonionic detergent extracts of these labeled cells. Specifically precipitated radiolabeled molecules were identified using sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. Sera from five of seven pemphigus patients specifically precipitated (from extracts of both Pam cells and human epidermal cells) a molecule that, when reduced, was approximately 130 kD, whereas seven normal human sera and two pemphigoid sera did not precipitate this molecule. The findings that (a) these precipitated molecules comigrated on SDS-PAGE and that (b) the 130-kD molecule could no longer be precipitated from cell extracts that had been previously reacted with a pemphigus serum, indicate that reactive pemphigus sera bind the same molecule. The molecule was not detected in the culture medium of these cells. This finding, along with the cell surface immunofluorescence pattern, suggests that the antigen is bound to the cell surface. Cultured mouse and human fibroblasts do not synthesize the antigen. The antigen contains protein because it was degraded by V8 protease and chymotrypsin, and it could also be labeled with [(14)C]amino acids. It is probably not a sulfated proteoglycan because it did not label with (35)SO(4). Taken together, these data indicate that some, but not all, pemphigus sera bind a specific cell surface glycoprotein that is synthesized by keratinocytes.

Bullous eruption of systemic lupus erythematosus. Dramatic response to dapsone therapy.

Four patients with systemic lupus erythematosus developed a nonpruritic vesiculobullous eruption that was unresponsive to high-dose systemic corticosteroid therapy. In three patients the eruption was not associated with a flare of systemic disease. Biopsy results showed neutrophilic microabscesses at the dermal papillary tips and perivascular lymphohistiocytic infiltrates. Direct immunofluorescence of normal appearing skin not exposed to the sun was positive in all four patients. Due to the unresponsiveness to corticosteroid therapy and the striking histologic resemblance to dermatitis herpetiformis, each of the patients was treated with dapsone. Within 24 hours each patient had prompt cessation of the appearance of new lesions. Improvement of the eruption did not correlate with improvement of the systemic manifestations of their lupus erythematosus. The rapid response to dapsone therapy suggests that dapsone is useful in treating bullous lesions of systemic lupus erythematosus.

Herpes gestationis. Immunopathology and characterization of the HG factor.

Five patients with herpes gestationis, a blistering disease of pregnancy, were studied immunologically. All had in vivo deposition of C3 in a linear band along the basement membrane zone of lesional and normal-appearing skin, the location of early blister formation. Immunoglobulin deposition was more variable, though four patients had evidence of in vivo bound IgG at the same site. A circulating, complement binding herpes gestationis factor was demonstrated in the sera of four of the patients, its concentration unrelated to the activity of clinical disease. Characterization of this factor by sucrose gradient ultracentrifugation, specific absorption studies, and papain digestion indicates that it is an IgG. Evidence exists for involvement of both the classical and alternate complement pathways in vivo, though in vitro studies implicate the classical pathway as the primary route of complement activation. Three offspring were studied, none with clinical involvement; one showed in vivo deposition of C3 at the basement membrane zone of normal skin and a second showed the herpes gestationis factor in cord blood.