Dendritic cells (DC) play a key role in the immunological reactions throughout the body. Dendritic cells (DC) and their immature counterparts, Langerhans cells (LC), are highly specialized antigen-presenting cells (APC) located in the skin, mucosa, and lymphoid tissues. DC and LC play a key role in the induction phase of contact allergenicity, and it is likely that these cells can be used to develop in vitro assays for contact sensitization and other immunological reactions of the body.
Dendritic cells (DCs) are potent antigen presenting cells (APCs) that possess the ability to stimulate naïve T cells. They comprise a system of leukocytes widely distributed in all tissues, especially in those that provide an environmental interface. DCs posses a heterogeneous haemopoietic lineage, in that subsets from different tissues have been shown to posses a differential morphology, phenotype and function. The ability to stimulate naïve T cell proliferation appears to be shared between these various DC subsets. It has been suggested that the so-called myeloid and lymphoid-derived subsets of DCs perform specific stimulatory or tolerogenic function, respectively. DCs are derived from bone marrow progenitors and circulate in the blood as immature precursors prior to migration into peripheral tissues. Within different tissues, DCs differentiate and become active in the taking up and processing of antigens (Ags), and their subsequent presentation on the cell surface linked to major histocompatibility (MHC) molecules. Upon appropriate stimulation, DCs undergo further maturation and migrate to secondary lymphoid tissues where they present Ag to T cells and induce an immune response. DCs are receiving increasing scientific and clinical interest due to their key role in anti-cancer host responses and potential use as biological adjuvants in tumour vaccines, as well as their involvement in the immunobiology of tolerance and autoimmunity.
Dendritic cells (DCs), originally identified by Steinman and his colleagues (1972) represent the pacemakers of the immune response.1 They are crucial to the presentation of peptides and proteins to T and B lymphocytes and are widely recognized as the key antigen presenting cells (APCs). They are critical for the induction of T cell responses resulting in cell-mediated immunity (CMI). The T cell receptors (TCRs) on T lymphocytes recognize fragments of antigens (Ags) bound to molecules of the major histocompatibility complex (MHC) on the surfaces of APCs. The peptide binding proteins are of two types, MHC class I and II, which interact with and stimulate cytotoxic T lymphocytes (CTLs) and T helper cells (Ths), respectively. On entry into APCs, Ags are processed, spliced into peptides in the cytosol and then reexpressed on the cell surface linked to MHC proteins. When bound to MHC class I molecules, CTLs are generated and activated and cells in tissues expressing the Ags (e.g. virus infected cells, cancer cells) are recognised and destroyed. Antigens reexpressed on the cell surface linked to MHC class II molecules interact with Th cells which when activated have profound immune-regulatory effects.2 Thus, DCs play a key role in host defenses and a crucial role in putative anti-cancer immune responses.
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