A class of major histocompatibility complex wherein the histocompatibility antigens are expressed on the surface of major antigen-presenting cells such as macrophages, B cells, and dendritic cells, and are then recognized by CD4 co-receptors
Major histocompatibility complex (acronym: MHC) refers to a cluster of genes that specify for major histocompatibility antigens expressed on the surface of the cell. In essence, epitopes (a fragment of protein that the cell displays on its surface) serve as MHC molecules that the immune cells use to distinguish self from non-self and then immunologically respond accordingly. MHCs are of three classes: MHC class I, MHC class II, and MHC class III.
Major histocompatibility complex class II (MHC class II) is the class of MHC that expresses MHC molecules (antigens) made up of two chains, α and β. Each chain is made up of two domains. One of these two domains on each chain is a transmembrane domain that anchors the MCH class II antigen to the cell membrane. MHC class II antigen is recognizable only by the CD4 co-receptor, such as that of helper T cells (compare: MHC class I).
MHC class II antigens are found on professional antigen-presenting cells: macrophages, B cells, and dendritic cells.
- MHC class II