blood_and_immune_upper_slim capable of professional antigen presenting cell A cell capable of processing and presenting lipid and protein antigens to T cells in order to initiate an immune response. Professional antigen presenting cells, also known as APCs, are essential orchestrators of adaptive immunity. These cells possess the abilities to capture and process antigens and constitutively express MHC class II molecules to facilitate antigen presentation. These cells are able to deliver the three signals to activate naïve T cells, thereby initiating adaptive immunity. Professional APCs include dendritic cells, macrophages, and B cells. Among these, dendritic cells are often considered the predominant APC as they have been demonstrated to activate naïve T cells. Macrophages and B cells also possess antigen-processing machinery and constitutively express MHC class II molecules. Dendritic cells and macrophages obtain antigens via phagocytosis of cells and cell debris, while B cells obtain antigens via the B cell receptor. APCs are responsible for stimulating an appropriate immune response. Following antigen presentation (signal 1), they deliver costimulatory signals (signal 2) and secrete mediators such as cytokines (signal 3) that shape the subsequent immune response. APCs can also induce tolerogenic responses to self-antigens. APCs play important roles in diseases such as cancer and autoimmune diseases. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) APC https://cellxgene.cziscience.com/cellguide/CL_0000145 Note change of name; nearly all somatic cells can present antigens to T cells via MHC Class I complexes leading to effector responses, but professional antigen presenting cells constitutively express MHC Class II as well as costimulatory molecules, and thus can initiate immune responses via T cells. ZFA:0009088 leukocyte antigen processing and presentation of peptide or polysaccharide antigen via MHC class II