Recombinant Rat Lymphotactin/XCL1, also known as lymphotactic factor, is the sole member of the C-type chemokine family. It is primarily produced by CD8+ T cells and natural killer cells. Unlike other chemokines, Recombinant Rat Lymphotactin/XCL1 possesses unique sequence features and two interconvertible protein conformations, which contribute to its distinct functions. The specific receptor for XCL1, XCR1, belongs to the G-protein coupled receptor family. The interaction between XCL1 and XCR1 plays a crucial role not only in negative selection and establishment of self-immune tolerance in the thymus but also in cross-presentation of antigens and mediation of cytotoxic immune responses. Recombinant Rat Lymphotactin/XCL1 is involved in immune system regulation, maintenance of intestinal immune homeostasis, and is associated with various diseases such as autoimmune diseases, nephritis, tuberculosis, and human immunodeficiency virus infection. Recent studies have shown that XCR1 is selectively expressed on CD8+ dendritic cells with antigen-presenting ability, leading to numerous applications and promising results in the field of Recombinant Rat Lymphotactin/XCL1-related research, including mucosal immunity, anti-tumor immune therapy, and targeted vaccine development.
The gene encoding human C-type chemokine XCL1 is located on chromosome 1 and consists of three exons and two introns. The first exon encodes the signal peptide, while the third exon encodes a product highly homologous to C C chemokines. There is an E1 promoter sequence upstream of the transcription start site, and multiple transcription factor binding sites, including NF-κB/c-REL, TCF2/ETS-1/PEA3, and TATA box, are distributed between the promoter and the transcription start site. The mouse Recombinant Rat Lymphotactin/XCL1 gene is also located on chromosome 1 and is linked to genes such as FasL, At3, Sele, and Otf1.
Although the upstream transcription factor binding sites similar to humans are present in the transcription start site of mouse Recombinant Rat Lymphotactin/XCL1, the regulatory region of mouse Recombinant Rat Lymphotactin/XCL1 is more similar to IL-8 in terms of the spacing between transcription factor binding sites. Another difference is that the 3' untranslated region of humans contains two or more polyadenylation signal sequences, while mice have only one polyadenylation signal sequence. The mouse XCL1 mRNA is 0.9 kb long, encoding a precursor of 114 amino acids. After signal peptide cleavage, it becomes 93 amino acids in size with a molecular weight of only 10 kDa. Humans have two homologous isoforms, XCL1 and XCL2 (also known as SYC1 and SCYC2), which differ by only two amino acids.
Compared to other chemokine families, Recombinant Rat Lymphotactin/XCL1 has two notable structural features:
1. Lack of the first and third conserved cysteine residues, forming only one disulfide bond between the second and fourth cysteine residues;
2. Possession of a C-terminal mucin-like domain that is 20-30 amino acids longer than other chemokines.
[1] Buyong J, Lubkowski J, Nussinov R. Homology modeling and molecular dynamics simulations of lymphotactin. Protein Sci 2000; 9: 2192-2199 [PMID: 11152129 DOI: 10.1110/ps.9.11.2192]
[2] Research Progress on C-type Chemokine XCL1. Yu Lei
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