Friedhelm Steckel

In vitro model for contact sensitization: I. Stimulatory capacities of human blood-derived dendritic cells and their phenotypical alterations in the presence of contact sensitizers.

Dendritic cells (DC) are highly specialized antigen-presenting cells (APC) located in many non-lymphoid tissues and a specialized form of DC-the Langerhans cell (LC)-is found in the skin. The functionality of LC as APC is crucial for the induction of an allergic contact dermatitis. For a long time LC research has been hampered by the limiting numbers of functionally active LC that could be isolated from human skin. The addition of GM-CSF and IL-4 to the non-adherent fraction of mononuclear cells from peripheral blood generated a large amount of CD1a(+) HLA-DR(+) DC. These in vitro-generated DC exhibited the morphology, phenotype and autologous T-lymphocyte stimulating capacity of the human DC/LC system. We had tested phenotypical alterations of in vitro-generated DC under the influence of subtoxic concentrations of different chemicals and contact sensitizers. In vitro stimulation with the contact sensitizers urushiol, primin, C10-and C11-primin analogues, alantolactone, isoalantolactone and NiSO(4) resulted in a decrease of HLA-DR expression on the surface of these cells if the incubation period did not exceed 3 hr. Incubation with irritants like sodium lauryl sulfate (SLS) and benzalkonium chloride did not change or increase the HLA-DR surface expression under these conditions. With regard to the adhesion molecule ICAM-1, there was no clear difference between irritants and contact sensitizers. But based on the alteration of HLA-DR expression of dendritic cells under short-term exposure conditions, there was a clear-cut difference between irritants and contact sensitizers. In summary, this system can be used to discriminate between contact sensitizers and irritants.

Phenotype and Alloactivating Capacity of Dendritic Cells Generated under Different Culture Conditions from Human Peripheral Blood

Dendritic cells (DCs) are a family of specialized cells distributed in various tissues with stimulatory capacities for primary and secondary immune responses especially by antigen presentation to T-lymphocytes. The isolation of skin associated DCs from skin biopsies is hampered by the limited numbers of DCs and tedious isolation procedures. Recently, several investigators described procedures for the in vitro generation of cells with the feature of DCs/Langerhans cells (LCs) from human peripheral blood to have sufficient numbers of cells to investigate the characteristics of the cells (Caux et al., 1992; Thomas et al., 1993; Sallusto and Lanzavecchia, 1994).

Antigen Presenting and Primary in Vitro Sensitizing Capacity of CD1a+ Dendritic Cells Generated from Human Blood

Dendritic cells (DCs) are highly specialized antigen presenting cells (APCs) initiating primary T-lymphocyte associated immune responses1. DCs are located in many non-lymphoid tissues and a specialized form of DCs - the Langerhans cells (LCs) - is found in the skin. Here they fulfill their in vivo functions by capturing antigens in the epidermis and presenting these antigens to T-lymphocytes in a HLA-restricted way2. Until now the small numbers of functional active LCs which could be isolated from human skin were the limiting factor in this field of research3.