CD85

CD85, also known as leukocyte immunoglobulin-like receptor subfamily B member 2 (LILRB2), is a protein that belongs to the immunoglobulin superfamily. It is primarily expressed on the surface of immune cells, including natural killer (NK) cells, monocytes, and macrophages. CD85 plays a crucial role in regulating immune responses and maintaining immune homeostasis.

Structure and Function

CD85 is a type I transmembrane protein consisting of an extracellular domain, a transmembrane region, and a cytoplasmic tail. The extracellular domain contains multiple immunoglobulin-like domains, which are responsible for ligand binding. The cytoplasmic tail contains immunoreceptor tyrosine-based inhibitory motifs (ITIMs), which mediate inhibitory signaling upon ligand binding.

CD85 interacts with a variety of ligands, including major histocompatibility complex (MHC) class I molecules, human leukocyte antigen (HLA)-G, and other unknown ligands. Binding of CD85 to its ligands leads to the recruitment of phosphatases, such as SHP-1 and SHP-2, to the ITIMs, resulting in the inhibition of immune cell activation and effector functions.

Role in Immune Regulation

CD85 is primarily known for its inhibitory role in immune regulation. By binding to MHC class I molecules, CD85 can recognize self from non-self cells. This interaction helps prevent the activation of immune cells against healthy, self-tissues. CD85 also interacts with HLA-G, a non-classical MHC class I molecule that is expressed in certain immune-privileged sites, such as the placenta. This interaction is thought to play a role in maternal-fetal tolerance during pregnancy.

In addition to its inhibitory function, CD85 has been implicated in modulating immune responses in various disease settings. For example, CD85 expression on NK cells has been shown to be upregulated in certain viral infections, such as HIV and hepatitis C virus (HCV). This upregulation may contribute to the dysfunction of NK cells and the evasion of immune surveillance by the viruses.

Clinical Implications

Given its role in immune regulation, CD85 has emerged as a potential therapeutic target for various diseases. For instance, blocking CD85 interactions with its ligands could enhance immune responses against cancer cells, as tumor cells often exploit inhibitory receptors like CD85 to evade immune recognition. Several studies have investigated the use of CD85-blocking antibodies or soluble CD85 molecules as immunotherapeutic agents.

Furthermore, CD85 expression levels on immune cells have been proposed as biomarkers for certain diseases. For example, increased CD85 expression on NK cells has been associated with poor prognosis in patients with certain types of cancer. Monitoring CD85 expression could help predict disease progression and guide treatment decisions.

See Also

• Natural Killer Cells
• Major Histocompatibility Complex
• Immunotherapy

References

1. Colonna M, Navarro F, Bellón T, et al. A common inhibitory receptor for major histocompatibility complex class I molecules on human lymphoid and myelomonocytic cells. J Exp Med. 1997;186(11):1809-1818. doi:10.1084/jem.186.11.1809 2. Lebbink RJ, de Ruiter T, Adelmeijer J, et al. Collagens Are Functional, High Affinity Ligands for the Inhibitory Immune Receptor LAIR-1. J Exp Med. 2006;203(6):1419-1425. doi:10.1084/jem.20052454 3. Zhang JQ, Nicoll G, Jones C, et al. Identification of the soluble form of LAIR-1 as a determinant of lymphocyte egress from lymphoid organs. Eur J Immunol. 2008;38(3):780-789. doi:10.1002/eji.200737758

This article is a stub related to medicine. You can help WikiMD by expanding it!