Antigen presenting cell

Antigen-presenting cells (APCs) are a heterogeneous population of cells with extraordinary immunostimulatory capacity. Some play an important role in the induction of the function of T helper cells and some communicate with other lymphocytes. Cytokines can render the ability to present antigens to various cell types. This results in the expression of MHC class II molecules, which are sometimes lacking on some cells such as endothelial cells. The different types of APCs include macrophages, dendritic cells, B cells and interdigitating cells. APCs are mostly derived from bone marrow and are distributed in lymphoid tissues and in the skin. These three types of major APCs are also called professional APCs. 

Also termed the mononuclear phagocytic system, monocytes circulate in the blood and macrophages in the tissues. In the bone marrow during hematopoiesis, the 

Dendritic cells are very important APCs along with mononuclear phagocytes. They are distributed in small quantities in various tissues that come in contact with the external environment including the skin, inner lining of the nose, lungs, stomach and intestine. The blood contains immature dendritic cells. After activation, dendritic cells migrate to the lymphoid tissue to initiate an acquired response following their interaction with lymphoid cells, B and T cells. There are two most common types 

Circulating dendritic cells Langerhans cells Interdigitating dendritic cells Interstitial dendritic cells Blood, lymph Skin, mucous membrane Secondary lymphoid tissue (with T cells), thymus Gastrointestinal tract, heart, liver, lungs, kidney 

Presence of CD la molecules on cell surface Augmented expression of MHC class II molecules A lack or very low expression of costimulatory molecules IL-10 inhibits maturation 

---

Interfaces play a predominant role in metabolic processes [78], as well as in immune recognition (e.g. T lymphocytes recognizing antigens on the surface of antigen presenting cells, section c2.14.6.2. Historically, the bulk of experimental... 

Antigen-presenting cells (APCs) are cells of the immune system that are able to process and present foreign antigens to effector cells. The antigen is presented in the context of an MHC-I or MHC-II molecule on APCs in the presence of so-called costimulatory molecules to activate the effector cells. 

Autoimmune Disease. Figure 1 Mechanisms of self tolerance. DC, dendritic (antigen presenting) cell T, T-lymphocyte Th, T helper lymphocyte Treg, T regulatory lymphocyte. For details see text. 

Autoimmune Disease. Figure 2 Generation of autoreactivity. APC, antigen presenting cell IFN, interferon LPS, lipopolysaccharide MHC, major histocompatibility complex T, T-lymphocyte TCR, Tcell (antigen) receptor TLR, toll like receptors. For details see text. 

Dendritic cells (DC) are important antigen-presenting cells mostly derived from the bone marrow. Microscopically they show characteristic long cytoplasmic extensions called dendrites. There are several types of specialized DC present in all lymphoid tissues and major... 

Parallel to orchestrating acute inflammatory processes by providing an optimal milieu of cytokines, mediators, and adhesion molecules in order to recruit and activate effector cells to the site of infection, dendritic cells also setve as professional antigen-presenting cells for cells of the adaptive immune system ( antigen presentation ... 

In the specialized environment of secondary lymphoid tissues such as lymph nodes or spleen, dendritic cells provide the requirements for naive T-lymphocytes to become activated and to proliferate. The professional antigen-presenting cells present peptides in MHC II, express costimulatory molecules, and release cytokines into the immunological synapse, which is formed by the antigen-presenting cell and the naive T-lymphocyte. Thus, cells of innate immunity initiate and facilitate the activation of naive lymphocytes, and it is easily conceivable that their cytokines and adhesion molecules will instruct the naive T-lymphocyte during activation and differentiation to T-effector cells. 

Inhibit the interaction between antigen or antigen-presenting cells (AJPCs) and T-lymphocytes... 

Inhibitors of Interaction between Antigen or Antigen-Presenting Cells and T-Lymphocytes... 

Class IIHLA molecules are expressed on the surface of antigen-presenting cells. They play a key role in presentation of processed linear peptide antigens of at least nine amino acids to T cells. Antigen is bound to the HLA antigen binding cleft formed by the a and 3 chains of the HLA class II molecule. This tri-molecular HLA-antigen complex binds in turn to the variable portion of the T-cell receptor. 

The T cell receptor is a clonotypic, T cell specific surface receptor that mostly recognizes peptides bound to MHC molecules on antigen-presenting cells. 

Stingl G. Maurer D IgE-mediated allergen presentation via FceRI on antigen-presenting cells. Int Arch Allergy Immunol 1997 113 24-29. 

Medzhitov R Basophils function as antigen-presenting cells for an allergen-induced T-helper type 2 d 1 response. Nat Immunol 2009 10 713-720. 

Dendritic cells (DCs) are functionally classified into myeloid (MDCs) and plasma-cytoid DCs (PDCs), both of which are potent professional antigen presenting cells (APC) but vary in the expression of a number of surface molecules. They also exhibit differences in their susceptibility to various strains of HIV-1 (Lore et al. 2005 Smed-Sorensen et al. 2005). Their role in the dissemination of HIV-1 is of... 

Class 2 MHC molecules are expressed on the surface of B cells, macrophages, monocytes, various antigen-presenting cells (APCs) and certain cells of the T-cell famify. 

---