Armstrong P B, Quigley J P
Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Dev Comp Immunol. 1999 Jun-Jul;23(4-5):375-90. doi: 10.1016/s0145-305x(99)00018-x.
All animals and plants have immune systems that protect them from the diversity of pathogens that would otherwise threaten their survival. The different components of the immune system may inactivate the pathogens themselves or promote the inactivation and clearance of toxic products produced by the pathogens. An important category of virulence factors of bacterial and prokaryotic pathogens are the proteases, which act to facilitate the invasion of the pathogens and to promote their destructive growth in the host organism. The present review concentrates on the comparative biology of an evolutionarily conserved arm of the immune system, the protein, alpha2-macroglobulin. alpha2-Macroglobulin is an abundant protein of the plasma of vertebrates and members of several invertebrate phyla and functions as a broad-spectrum protease-binding protein. Protease-conjugated alpha2-macroglobulin is selectively bound by cells contacting the body fluids and alpha2-macroglobulin and its protease cargo are then internalized and degraded in secondary lysosomes of those cells. In addition to this function as an agent for protease clearance, alpha2-macroglobulin binds a variety of other ligands, including several peptide growth factors and modulates the activity of a lectin-dependent cytolytic pathway in arthropods.
所有动植物都有免疫系统，保护它们免受各种病原体的侵害，否则这些病原体会威胁它们的生存。免疫系统的不同组成部分可能会使病原体本身失活，或促进病原体产生的有毒产物的失活和清除。细菌和原核病原体的一类重要毒力因子是蛋白酶，其作用是促进病原体的入侵，并促进它们在宿主体内的破坏性生长。本综述着重于免疫系统中一个进化上保守的部分——蛋白质α2-巨球蛋白的比较生物学。α2-巨球蛋白是脊椎动物血浆以及几个无脊椎动物门成员体内的一种丰富蛋白质，作为一种广谱蛋白酶结合蛋白发挥作用。与蛋白酶结合的α2-巨球蛋白被接触体液的细胞选择性结合，然后α2-巨球蛋白及其携带的蛋白酶在这些细胞的次级溶酶体中被内化并降解。除了作为蛋白酶清除剂的功能外，α2-巨球蛋白还能结合多种其他配体，包括几种肽生长因子，并调节节肢动物中凝集素依赖性细胞溶解途径的活性。
