A comparison of murine epidermal Langerhans cells with spleen dendritic cells

Granulocyte/macrophage colony-stimulating factor is essential for the viability and function of cultured murine epidermal Langerhans cells

A panning method has been developed to enrich Langerhans cells (LC) from murine epidermis. In standard culture media, the enriched populations progressively lose viability over a 3-d interval. When the cultures are supplemented with keratinocyte-conditioned medium, LC viability is improved and the cells increase in size and number of dendritic processes. Accessory function, as monitored by stimulating activity in the mixed lymphocyte reaction (MLR), increases at least 10-20-fold. The conditioned media of stimulated macrophages and T cells also support the viability and maturation of cultured LC. A panel of purified cytokines has been tested, and only granulocyte/macrophage colony-stimulating factor (GM-CSF) substitutes for bulk-conditioned medium. The recombinant molecule exhibits half-maximal activity at 5 pM. Without activity are: IL-1-4; IFN-alpha/beta/gamma; cachectin/TNF; M- and G-CSF. A rabbit anti-GM-CSF specifically neutralizes the capacity of keratinocyte-conditioned medium to generate active LC. However, GM-CSF is not required for LC function during the MLR itself. We conclude that the development of immunologically active LC in culture is mediated by GM-CSF. The observation that these dendritic cells do not respond to lineage-specific G- and M-CSFs suggests that LC represent a distinct myeloid differentiation pathway. Because GM-CSF can be made by nonimmune cells and can mediate the production of active dendritic cells, this cytokine provides a T-independent mechanism for enhancing the sensitization phase of cell-mediated immunity.

Distribution and turnover of Langerhans cells during delayed immune responses in human skin

The changes in distribution and turnover of T6+ Langerhans cells (LC) in the skin during delayed immune responses to tuberculin, and in the lesions of tuberculoid leprosy and cutaneous Leishmaniasis were investigated. In each situation, there was a dermal accumulation of monocytes and T cells and epidermal thickening with keratinocyte Ia expression. In the tuberculin response a dramatic change in the distribution of LC was observed. By 41 h, T6+ LC were displaced to the upper zone of the thickening epidermis followed by an almost complete loss of LC from the epidermis by approximately 72 h. After 7 d, T6+ cells started to reappear in the epidermis, which regained almost normal numbers of T6+ LC by 14 d. After antigen administration and initiation of the delayed immune response, enhanced numbers of T6+ cells appeared in association with the mononuclear cell infiltrate of the upper dermal lesions. Their numbers peaked by 72 h, were reduced at 7 d, and again enhanced by 14 d, when the epidermis was being repopulated. Similar numbers of T6+ cells were found in the chronic lesions of tuberculoid leprosy and cutaneous Leishmaniasis but not lepromatous leprosy. The cells of the dermis were identified as typical LC by the presence of Birbeck granules and surface T6 antigen at the electron microscope level. These cells were closely associated with lymphocytes. We have quantified the number of LC, evaluated their directional flux into the epidermis and dermis, determined nearest neighbors, and made predictions as to their fate.

The ultrastructure of human gingival Langerhans cells in health and disease

There was a statistically significant shift towards increased proportions of type I Langerhans cells (containing many Langerhans-cell granules) and reduced proportions of both type II Langerhans cells (containing few granules) and indeterminate cells in diseased oral epithelium when compared to healthy oral epithelium. Langerhans cells and indeterminate cells were also seen in the sulcular epithelium of healthy and diseased specimens but never in junctional or pocket-lining epithelium.

The role of Langerhans cells in antigen presentation

Epidermal Langerhans cells are dendritic bone marrow-derived cells which synthesize and express Ia antigens. During the past decade, in vitro studies have demonstrated that they play a critical role in the induction of many types of T-cell responses. Specifically, Langerhans cells are effective antigen-presenting cells in allogeneic and antigen specific proliferative and cytotoxic T-cell responses. This paper reviews these functions and suggests areas of future investigations into the mechanisms involved in T-cell activation by Langerhans cells.