Clinical application of limitin that has anti-tumor and anti-viral activity

limittin是一种干扰素（IFN）样细胞因子，与先前已知的I型IFN具有序列同源性，并利用IFN-α/β受体发挥其生物活性。利用建立的抗限制蛋白抗体和重组限制蛋白，比较了限制蛋白与IFN-α的生物学功能，并分析了限制蛋白在体内的表达。(1)限药素增强了细胞毒性T淋巴细胞的杀伤活性和MHC I类分子的表面表达。限制蛋白稳定抑制p210bcr/abl转染的FDCP-1细胞的增殖。限制素还能诱导对EMCV、MHV和HSV的抗病毒状态。虽然上述限制蛋白的功能与IFN-α相似，但抑制CFU-IL7或CFU-Meg集落形成需要比IFN-α更高的限制蛋白浓度。限菌素对CFU-GM和BFU-E菌落形成无抑制作用，而IFN-α有抑制作用。这些数据表明，与其他干扰素相比，利格汀的毒性可能更小，因此可能在治疗I型干扰素已被证明有用的疾病方面具有独特的临床优势。(2)免疫组化分析表明，该蛋白是由健康小鼠脾脏和胸腺成熟T淋巴细胞产生的。结果表明，人胸腺cDNA是筛选人类局限性同源基因的合适cDNA文库来源。(3)酪氨酸激酶Tyk2的破坏完全取消了IFN-α-诱导的对CFU-IL7和CFU-Meg集落形成的抑制以及DAXX的上调和易位。这些数据表明Tyk2在IFN介导的骨髓抑制中起重要作用，我们现在正在分析limtin和IFN-α之间信号通路的差异。

Limitin is an interferon (IFN)-like cytokine that has sequence homology with previously known type I IFNs and utilizes the IFN-α/β receptor for its biological activities. Using our established the anti-limitin antibody and recombinant limitin protein, we compared biological functions between limitin and IFN-α, and analyzed in vivo expression of limitin protein. (1) Limitin augmented the killer activity of cytotoxic T lymphocytes as well as the surface expression of MHC class I molecules. Limitin inhibited the proliferation of FDCP-1 cells stably transfected with p210bcr/abl. Limitin also induced antiviral state against EMCV, MHV, and HSV. Although the above functions of limitin were similar to those of IFN-α, higher concentration of limitin was required than IFN-α for the inhibition of CFU-IL7 or CFU-Meg colony formation. Limitin could not inhibit CFU-GM or BFU-E colony formation while IFN-α did. These data suggest that limitin may be less toxic than other IFNs, and therefore may have a uniqueclinical niche for treatment of diseases where type I IFNs have proven useful. (2) Immunohistochemical analysis revealed that the limitin protein is produced by mature T lymphocytes in spleen and thymus in healthy mice. This result propose that cDNA from human thymus is a suitable source of cDNA library to screen human homolog of limitin. (3) The disruption of tyrosine kinase Tyk2 completely abrogated IFN-α-induced inhibition of CFU-IL7 and CFU-Meg colony formation as well as up-regulation and translocation of DAXX. These data indicate that Tyk2 plays an important role in IFN-mediated myelosuppression, and we are now analyzing the difference of signaling pathways between limitin and IFN-α.