- Interleukins interact with their specific receptors located within the cell membranes. Overall, the process of differentiation and proliferation of immune cells is followed by the change of species composition of their membrane molecules.
- All of these receptor molecules are immune phenotype markers of a particular cell line, which appear at a certain stage of cell development.
- These molecules were named as CD molecules or CD antigens (abbreviates from clusters of differentiation or clusters of designation).
- More than 370 of CD members are known to date.
The most important molecules with established functions are described below.
- – CD1 – expressed by cortical thymocytes, some dendritic cells; it takes part in lipid antigen recognition and presentation;
- – CD2 – common T cell marker, adhesion molecule, also expressed by NK cells, the receptor for sheep red blood cells; provides T cells rosette formation;
- – CD3 – a marker of all maturated T cells, supportive molecule for antigen-specific T cell receptor (TCR), participates in signal transmission via T cell receptor;
- – CD4 – T helper marker, human immunodeficiency virus (HIV) cell receptor, takes part in recognition of the antigen in complex with HLA II-class molecules by T helper cells;
- – CD5 – a marker of particular B cell subpopulations, albeit T cells also express this antigen;
- – CD8 – a marker of cytotoxic T cells, participates in recognition of the antigen in complex with HLA I-class molecules by cytotoxic T cells;
- – CD14 – expressed by monocyte-macrophage and granulocyte lineages, the receptor for complex “bacterial lipopolysaccharide–lipopolysaccharide-binding protein”; activation of the cells via CD14 leads to massive pro-inflammatory cytokine release;
- – CD16 – the antigen of neutrophils and NK cells; the low-affinity receptor to IgG antibodies (Fcγ RIII);
- – CD11/18 – leukocyte integrin, presented on lymphoid and myeloid cells;
- – CD19-CD22 – B cell markers;
- – CD25 – IL-2 receptor chain on lymphocyte membranes;
- – CD28 – costimulatory molecule for successful activation of T cells; binds to its counterparts CD80 and CD86 upon the membranes of antigen-presenting cells;
- – CD32 (Fcγ RII) – born by monocytes and neutrophils; it is the medium-affinity receptor to IgG;
- – CD34 – an early marker of hematopoietic stem cells;
- – CD35 – cellular receptor for C3b component of complement (CR1); it is expressed on many cell types (e.g., granulocytes and macrophages); it stimulates opsonization;
- – CD40 – a marker of maturated B cells; interacts with T cells via binding to CD40L (CD40 ligand or CD154) in B cell antigen presentation and cell activation;
- – CD45 – leukocyte common antigen; its molecular variation CD45RO – a marker of T memory cells; molecule CD45RA – a marker of naive T cells;
- – CD54 – adhesin ICAM-1 – intercellular adhesion molecule 1; it is the ligand for integrin CD11/CD18 expressed on lymphoid cells, monocytes and other cell types;
- – CD56 – a marker of natural killer (NK) cells; also present on some other cell types, including T cells;
- – CD62 – selectin molecule family, CD62P – platelet selectin, CD62E – endothelial, CD62L – leukocyte selectin; selectins pertain to the group of specialized adhesion molecules;
- – CD64 – high-affinity receptor to IgG antibodies (FcγRIII), expressed on monocytes, neutrophils, etc.
- – CD95 (Fas/Apo-receptor) – expressed by thymocytes, T- and B cell subsets, interacts with Fas-ligand or CD178, thereby activating programmed cell death (apoptosis);
- – CD152 – present on activated T lymphocytes; an inhibitory co-stimulatory molecule of T cells that binds to CD80 or CD86 and dampens activated T cells;
- – CD158 – expressed on natural killer cells, killer inhibitor receptor (KIR); suppresses NK cells activation on interaction with class I HLA molecules;
- – CD159 – present on natural killer cells, promotes their activation on interaction with class I HLA molecules