LILRA3

{{Short description|Protein-coding gene in the species Homo sapiens}}

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Leukocyte immunoglobulin-like receptor subfamily A member 3 (LILR-A3) also known as CD85 antigen-like family member E (CD85e), immunoglobulin-like transcript 6 (ILT-6), and leukocyte immunoglobulin-like receptor 4 (LIR-4) is a protein that in humans is encoded by the LILRA3 gene located within the leukocyte receptor complex on chromosome 19q13.4. Unlike many of its family, LILRA3 lacks a transmembrane domain. The function of LILRA3 is currently unknown; however, it is highly homologous to other LILR genes,{{cite journal | vauthors = Torkar M, Haude A, Milne S, Beck S, Trowsdale J, Wilson MJ | title = Arrangement of the ILT gene cluster: a common null allele of the ILT6 gene results from a 6.7-kbp deletion | journal = European Journal of Immunology | volume = 30 | issue = 12 | pages = 3655–62 | date = December 2000 | pmid = 11169408 | doi = 10.1002/1521-4141(200012)30:12<3655::aid-immu3655>3.0.co;2-y | doi-access = | s2cid = 38450831 }} and can bind human leukocyte antigen (HLA) class I. Therefore, if secreted, the LILRA3 might impair interactions of membrane-bound LILRs (such as LILRB1, an inhibitory receptor expressed on effector and memory CD8 T cells) with their HLA ligands, thus modulating immune reactions and influencing susceptibility to disease.{{cite journal | vauthors = Arm JP, Nwankwo C, Austen KF | title = Molecular identification of a novel family of human Ig superfamily members that possess immunoreceptor tyrosine-based inhibition motifs and homology to the mouse gp49B1 inhibitory receptor | journal = Journal of Immunology | volume = 159 | issue = 5 | pages = 2342–9 | date = September 1997 | doi = 10.4049/jimmunol.159.5.2342 | pmid = 9278324 | s2cid = 45021877 | doi-access = free }}{{cite journal | vauthors = Borges L, Hsu ML, Fanger N, Kubin M, Cosman D | title = A family of human lymphoid and myeloid Ig-like receptors, some of which bind to MHC class I molecules | journal = Journal of Immunology | volume = 159 | issue = 11 | pages = 5192–6 | date = December 1997 | doi = 10.4049/jimmunol.159.11.5192 | pmid = 9548455 | s2cid = 36907307 | doi-access = free }}{{cite web | title = Entrez Gene: LILRA3 leukocyte immunoglobulin-like receptor, subfamily A (without TM domain), member 3| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=11026}}

Like the closely related LILRA1, LILRA3 binds to both normal and 'unfolded' free heavy chains of HLA class I, with a preference for free heavy chains of HLA-C alleles {{cite journal | vauthors = Jones DC, Kosmoliaptsis V, Apps R, Lapaque N, Smith I, Kono A, Chang C, Boyle LH, Taylor CJ, Trowsdale J, Allen RL | title = HLA class I allelic sequence and conformation regulate leukocyte Ig-like receptor binding | journal = Journal of Immunology | volume = 186 | issue = 5 | pages = 2990–7 | date = March 2011 | pmid = 21270408 | doi = 10.4049/jimmunol.1003078 | doi-access = free }}