The immunologic properties of epidermal Langerhans cells as a part of the dendritic cell system

Abstract

Dendritic cells form a system of antigen-presenting cells that is widely distributed in the body. They constitute trace populations in lymphoid and non-lymphoid tissues and in the circulation. They are characterized by their typical dendritic and "veiled" morphology, by their constitutive expression of high levels of major histocompatibility complex class II molecules on their surface, and by their outstanding capacity to initiate primary immune responses. Dendritic cells occur in two states of differentiation. In the immature state they are highly specialized for processing foreign protein antigens; in the mature state they efficiently stimulate resting antigen-specific T cells. Dendritic cells can migrate from the non-lymphoid tissues, where they reside in the immature state, via the afferent lymphatics or the blood to the T cell-dependent areas of the lymphoid organs (lymph nodes, spleen). There, they appear as mature dendritic cells. Therefore, dendritic cells are ideally suited to mediate important aspects of immunogenicity: they can acquire antigens in the tissues and process them in an immunogenic form; they can carry the immunogen to the lymphoid organs; and they can find and efficiently activate antigen-specific T cell clones and thus generate an immune response. Studies of epidermal Langerhans cells have greatly helped in establishing this concept. They can be investigated freshly isolated from the epidermis where they represent immature (tissue) dendritic cells. After 2-3 days in culture they develop into mature dendritic cells. The mechanisms of dendritic cell maturation, which can be studied best using epidermal Langerhans cells, and the specific functions of Langerhans cells in immunogenicity are discussed.

Morphologically and functionally intact dendritic cells can be derived from the peripheral blood of aged individuals

“…They are highly specialized in antigen presentation, are the principal activators of resting T cells, and represent a major source of immunogenic epitopes after administration of antigen [2,3]. DC provide T cells with all necessary signals required for activation and proliferation.…”

Langerhans cells transport Leishmania major from the infected skin to the draining lymph node for presentation to antigen‐specific T cells

“…LC are members of tbe dendritic celllineage that forms a system of potent APC in lymphoid and nonlymphoid tissues [4][5][6][7]. Dendritic cells constitutively express high levels of MHC class II molecules and possess the unique capacity to induce primary T ceH responses.…”

Human Decidua Contains Potent Immunostimulatory CD83+ Dendritic Cells

“…9 Although there is considerable interest in DCs, working with these cells is hampered because of their low frequency in blood 15 and tissue. 16 Additionally, the lack of an antibody specific for the early stages of DCs makes identification and isolation of fresh DCs difficult. In vivo, a proportion of mature DCs may be stained in tissue sections using either the CD83 or CMFR-44 monoclonal antibodies.…”