Recombinant Human Xcl1 protein

XCL1 (chemokine (C motif) ligand 1), also known as lymphotactin, is a unique member of the chemokine family that plays a critical role in immune regulation. Unlike most chemokines classified into CXC or CC subfamilies, XCL1 belongs to the XC subfamily due to its singular cysteine motif (C). It is primarily secreted by activated CD8+ T cells, natural killer (NK) cells, and thymic dendritic cells, acting as a chemoattractant for immune cells expressing its receptor XCR1. which is predominantly found on cross-presenting dendritic cells (cDC1). This XCL1-XCR1 axis is crucial for coordinating adaptive immune responses, particularly in antiviral defense and antitumor immunity.

Recombinant XCL1 protein is engineered through genetic modification, typically using bacterial (e.g., E. coli) or mammalian expression systems. The protein’s native structure contains 114 amino acids, including a conserved chemokine domain and a C-terminal extension that influences receptor binding specificity. However, native XCL1 exhibits structural instability due to a dynamic equilibrium between monomeric and dimeric forms under physiological conditions. To address this, modified variants like "Ltn-II" (a stabilized mutant) have been developed for experimental and therapeutic applications.

Research applications of recombinant XCL1 include studying immune cell migration, dendritic cell-mediated antigen presentation, and tumor microenvironment modulation. Its therapeutic potential is being explored in cancer immunotherapy, particularly for enhancing dendritic cell recruitment to tumors. Challenges remain in maintaining its structural integrity and receptor specificity in vivo, prompting ongoing protein engineering efforts. Recent studies also highlight its role in vaccine adjuvant design and autoimmune disease regulation, underscoring its dual functionality as both a chemoattractant and an immune modulator.