Department of Pathobiological Sciences, School of Vet Medicine, University of Wisconsin-Madison, 2115 Observatory Drive (Biotron), Madison, Wisconsin 53706-1087.
Integr Comp Biol. 2003 Apr;43(2):305-12. doi: 10.1093/icb/43.2.305.
The involvement of circulating hemocytes as the principal cellular effector mediating molluscan immune responses is well established. They participate in a variety of internal defense-related activities including microbial phagocytosis, multicellular encapsulation, and cell-mediated cytotoxicity reactions that are presumed to be initiated through foreign ligand binding to hemocyte receptors and subsequent transduction of the binding signal through the cell resulting in appropriate (or in some cases, inappropriate) hemocyte responses. At present, however, although functional evidence abounds as to the existence of hemocyte "recognition" receptors, few have been characterized at the molecular level. Similarly, signal transduction systems associated with various receptor-mediated hemocyte functions in molluscs are only beginning to be investigated and understood. This review examines what is currently known about the molluscan hemocyte receptors and the putative signal transduction pathways involved in regulating their cellular behaviors/activities. The cumulative data implies the presence of various hemocyte-associated receptors capable of binding specific carbohydrates, extracellular matrix proteins, growth factors, hormones, and cytokines. Moreover, receptor-ligand interactions appear to involve signaling molecules similar to those already recognized in vertebrate immunocyte signal transduction pathways, such as protein kinases A and C, focal adhesion kinase, Src, Ca(2+) and mitogen-activated protein kinase. Overall, the experimental evidence suggests that molluscan immune responses rely on molecules that share homology with those of vertebrate signaling systems. As more information regarding the molecular nature of hemocyte recognition receptors and their associated signaling molecules is accumulated, a clearer picture of how hemocyte immune responses to invading organisms are regulated will begin to emerge.
循环血细胞作为介导软体动物免疫反应的主要细胞效应物的参与已得到充分证实。它们参与各种与内部防御相关的活动，包括微生物吞噬、多细胞包裹和细胞介导的细胞毒性反应，这些反应被认为是通过外来配体与血细胞受体结合，并通过细胞传递结合信号而引发的，导致适当的（或在某些情况下，不适当的）血细胞反应。然而，目前尽管有大量关于血细胞“识别”受体存在的功能证据，但很少有受体在分子水平上得到表征。同样，与各种受体介导的软体动物血细胞功能相关的信号转导系统也才刚刚开始被研究和理解。这篇综述考察了目前关于软体动物血细胞受体以及参与调节其细胞行为/活动的假定信号转导途径的了解。累积的数据表明存在各种能够结合特定碳水化合物、细胞外基质蛋白、生长因子、激素和细胞因子的血细胞相关受体。此外，受体-配体相互作用似乎涉及与已经在脊椎动物免疫细胞信号转导途径中识别出的相似的信号分子，如蛋白激酶 A 和 C、粘着斑激酶、Src、Ca(2+)和丝裂原激活蛋白激酶。总的来说，实验证据表明，软体动物的免疫反应依赖于与脊椎动物信号系统具有同源性的分子。随着关于血细胞识别受体及其相关信号分子的分子性质的更多信息的积累，关于血细胞如何对入侵生物体的免疫反应进行调节的更清晰的图景将开始浮现。
