LILRB3

Ideogram human chromosome 19

LILRB3 (Leukocyte Immunoglobulin-Like Receptor, Subfamily B (with TM and ITIM domains), member 3), also known as ILT5 (Immunoglobulin-like Transcript 5), is a protein that in humans is encoded by the LILRB3 gene. This gene is a member of the leukocyte immunoglobulin-like receptor (LIR) family, which is found on the surfaces of immune cells, including monocytes, dendritic cells, and B cells. LILRB3 plays a significant role in the regulation of the immune response, particularly in the modulation of inflammatory processes and the maintenance of immune tolerance.

Function

LILRB3 is an inhibitory receptor that recognizes class I Major Histocompatibility Complex (MHC) molecules. Upon binding to MHC class I molecules on target cells, LILRB3 transmits inhibitory signals into the immune cell, primarily through its Immunoreceptor Tyrosine-based Inhibitory Motifs (ITIMs) located in the cytoplasmic domain. This interaction leads to the downregulation of immune cell activation, serving as a mechanism to prevent excessive or inappropriate immune responses, including autoimmunity.

Clinical Significance

The expression and function of LILRB3 have been implicated in various clinical conditions, including autoimmune diseases, cancer, and infectious diseases. In the context of cancer, LILRB3 may contribute to the immune evasion of tumor cells by inhibiting the activation of immune cells that would otherwise target and destroy cancer cells. Conversely, in autoimmune diseases, the inhibitory function of LILRB3 can be beneficial in preventing or reducing tissue damage caused by an overactive immune response.

Genetics

The LILRB3 gene is located on human chromosome 19q13.4, within a cluster of other leukocyte receptor genes. The genetic variability within this locus can influence the expression and function of LILRB3, potentially affecting an individual's susceptibility to certain diseases or the severity of disease manifestations.

Research Directions

Ongoing research is focused on further elucidating the role of LILRB3 in the immune system and its potential as a therapeutic target. Strategies to modulate LILRB3 activity are being explored in the context of enhancing anti-tumor immunity or suppressing pathological immune responses in autoimmune diseases and transplantation.