Biomedical subjects

B Ferbel

Publications and source records attributed to B Ferbel.

6 recordsLinked to original sources

PubMed2000

The imidazoquinolines, imiquimod and R-848, induce functional, but not phenotypic, maturation of human epidermal Langerhans' cells.

Imiquimod (R-837) and its more potent derivative (R-848) are imidazoquinolines that have adjuvant activity in cultured human mononuclear cells. Its mechanism of action on epidermal antigen-presenting cells is not known. The purpose of the present investigation was to determine whether imiquimod and R-848 affect human epidermal Langerhans' cells' (LC) in vitro maturation. Pulse incubations (6-16 h) of cultured unfractionated epidermal cells or highly enriched LC suspensions with either imiquimod or R-848 (0. 05-5.0 microg/ml of culture medium) reproducibly enhanced their ability to induce T-cell proliferation in a primary mixed lymphocyte reaction. There was a 30 to 300% increase in T-lymphocyte proliferation induced by either imiquimod- or R-848-treated LC when compared to control, untreated LC. IFN-gamma secretion by T-lymphocytes stimulated by imiquimod- or R-848-treated LC was increased compared to control, untreated LC. After a 6-h incubation, phenotypic analysis of control-, imiquimod-, or R-848-treated LC indicated that such antigen-presenting cells were in an "intermediate" state of maturation (CD1a(+), HLA-DR, DP, DQ(bright+), CD40(low+), CD86(high+), and CD80(low+)). RNase protection assays demonstrated that either imiquimod or R-848 treatments increased steady-state transcripts encoding for IL-12 p40, IL-1beta, TNF-alpha, and IL-1 receptor antagonist by LC. These data indicate that imiquimod and R-848 dissociate the functional maturation (cytokine-mediated) and phenotypic maturation of epidermal LC. These data warrant further exploration for the use of imidazoquinoline-treated LC or other DC subsets for processing and presentation of viral peptides to Th-lymphocytes as a novel vaccine strategy to induce protective antiviral responses.

Adjuvants, Immunologic↗

PubMed2000

Allergens and irritants transcriptionally upregulate CD80 gene expression in human keratinocytes.

The human CD80 costimulatory molecule is an important signal between professional antigen-presenting cells and T helper cells. The immunobiology of CD80 expression by keratinocytes, especially during allergic and irritant contact dermatitis, however, is less well understood. CD80 cell surface expression and gene transcription by keratinocytes was increased when keratinocytes were exposed to certain allergens (chemicals that induce inflammation via hapten-specific T cells) and irritants (chemicals that are toxic to epidermal cells). Therefore, the human CD80 promoter was cloned and luciferase reporter constructs containing various promoter fragments were engineered. Promoter mapping of these CD80 constructs in transiently transfected keratinocytes showed that a construct containing the proximal 231 bp immediately upstream of the transcription start site of the CD80 promoter was most active in keratinocytes and was inducible to a level ranging from 2- to 10-fold higher in keratinocytes treated with certain allergens and irritants, compared with untreated keratinocytes. This pattern of promoter fragment activity in keratinocytes is identical to that found in professional antigen-presenting cells. This is the first demonstration that the CD80 promoter is active in keratinocytes and that this activity is further increased in keratinocytes treated with certain allergens and irritants. These data suggest that allergens and irritants may, in part, break peripheral tolerance by their direct effects on keratinocyte costimulatory molecule expression, thereby facilitating interactions with epidermotropic T helper cells via the CD80-CD28 or CTLA-4 pathways.

Allergens↗

PubMed1995

Human keratinocytes regulate their expression of B7/BB-1 antigen by a unique, calcium-dependent mechanism.

Previous studies of normal human keratinocytes have indicated that these cells express BB-1 antigen, an important adherence molecule usually associated with "professional" antigen-presenting cells. We studied freshly isolated epidermal cells and noted that the frequency of BB-1-positive cells in normal human skin varied from 2.6 to 7.4% of total epidermal cells. Two-color flow cytometry confirmed that keratinocytes were the major cell in the epidermis that expressed BB-1, because less than 10% of total epidermal Langerhans cells were positive for BB-1. Northern blot analysis of RNA extracted from normal human epidermis revealed low levels of 1.7-kb B7-1 transcripts, which were independent of the presence of epidermal Langerhans cells, again indicating that such transcripts were derived from keratinocytes. Keratinocytes cultured in medium containing low concentrations of extracellular calcium (0.07 mM) expressed low levels of cell-surface BB-1. However, keratinocytes cultured in medium with higher levels of extracellular calcium (1.5 mM) lost cell-surface expression of BB-1. Similarly, low-calcium keratinocytes expressed the 1.7- and 2.9-kb B7-1 transcripts, whereas high-calcium keratinocytes expressed only the 1.7-kb transcript. Studies of the cell-surface expression of BB-1 by plastic adherent monocytes indicated that such cells do not respond to similar changes in extracellular calcium concentrations. Calcium-induced differentiation of keratinocytes regulates the expression of BB-1 antigen as well as transcripts, which is a novel mechanism for the regulation of this molecule.

Adult↗

PubMed1994

Exaggerated and persistent cutaneous delayed-type hypersensitivity in transgenic mice whose epidermal keratinocytes constitutively express B7-1 antigen.

Since mouse keratinocytes are tolerogenic antigen presenting cells for T cell activation, the expression of second signal molecules such as B7-1 was targeted to epidermal keratinocytes (KC) in vivo in transgenic mice. The expression vector used to create transgenic mice consisted of a keratin 14 promoter fused 5' to the full length open reading frame of the cDNA encoding mouse B7-1 (between 10 and 30 copies of the transgene per genome). Expression of B7-1 cell surface protein was assessed by in situ immunostaining of cryostat sections of tail skin with CTLA-4/Ig fusion protein, revealing high levels of cell surface expression of B7 by all epidermal KC of transgenic mice, and a lack of such expression in nontransgenic animals. The skin of such transgenic mice (derived from three different founder mice) was grossly and histologically normal, with normal numbers of Langerhans cells and dendritic epidermal T cells. Immunologic challenge of transgenic mice with epicutaneous haptens such as fluorescein isothiocyanate revealed enhanced and persistent delayed-type hypersensitivity responses, with an altered kinetics of resolution when compared with nontransgenic controls. These data indicate that in normal, nontransgenic mice, tolerogenic antigen presentation by KC plays an important physiologic role in damping T cell-mediated inflammation in the skin by competing with professional APC for TCR occupancy in antigen specific T-lymphocytes that migrate into the epidermis. This also implies that altered regulation of B7-1 gene expression by epidermal cells may account for skin "hyperresponsiveness" encountered in some chronic dermatologic disorders.

Abatacept↗

PubMed1993

Accessory and alloantigen-presenting cell functions of A431 keratinocytes that stably express the B7 antigen.

Because keratinocytes are tolerogenic antigen-presenting cells (APC), we investigated the role of B7/BB-1 in reconstituting defective accessory cell (AC) and APC functions by such nonlymphoid cells. KC were induced to stably express B7/BB-1 by DNA-mediated gene transfection. This single-transformed B7/BB-1+ A431 cell line (but not control A431) functioned as AC for lectin-induced T-cell proliferation, as well as oxidative mitogenesis. This costimulation was dependent on B7/BB-1 expression since the monoclonal antibody BB-1 blocked costimulation of PHA mitogenesis by 75%. After the induction of class II MHC antigen expression by interferon-gamma, B7/BB-1+ KC but not control KC presented alloantigens to resting T-cells in the primary mixed lymphocyte reaction. These data indicate that the stable expression of B7/BB-1 antigen by KC reconstitutes defective AC and alloantigen-presenting activity. The lack of expression of such second signal by normal KC may be responsible for their ability to induce clonal anergy in vitro and in vivo.

Antigen-Presenting Cells↗

PubMed1993

Thy 1+ dendritic epidermal cells but not Langerhans cells express Ly 48.

Leukosialin (Ly 48) is a sialoprotein expressed by bone marrow-derived cells early in their development. To determine whether Ly 48 is expressed by specific subsets of epidermal cells (ECs) such as Langerhans cells, keratinocytes, or dendritic epidermal T cells (DETCs), we utilized flow cytometry to detect staining of ECs by a panel of four monoclonal antibodies (S11, S15, S7, and 3E8) that recognize two different epitopes of the leukosialin antigen. Approximately 2.0% of unfractionated ECs expressed Ly 48, as demonstrated by reactivity with the monoclonal antibodies S11 and S15. Similarly, immunoblots of unfractionated EC lysates revealed an antigen of 125 kD apparent molecular weight that reacted with the S11 monoclonal antibody. Enrichment or depletion of various EC populations indicated that DETCs are the only EC population that express Ly 48. Studies of long-term cultured DETC lines indicated a marked heterogeneity of expression of Ly 48 epitopes. The function(s) of Ly 48 on DETCs as well as T-cell receptor alpha/beta bearing mouse T cells remains to be determined.

Animals↗