Functional Studies of Chicken Histocompatibility Antigens Bearing Ig V-like Domains

最近，在确定鸡主要组织相容性复合体中编码的高度多态性B-G抗原的结构方面取得了重大进展。已经确定B-G抗原是一个分子家族，其不同的成员在红细胞以外的几种不同组织的细胞上表达，包括免疫系统细胞。对某些B-G家族成员序列的测定揭示了B-G多态性的结构基础，包括免疫球蛋白v样结构域内高变序列多样性的存在。B-G细胞质尾部由不同序列的7个重复片段组成。在肠道上皮细胞、肝脏细胞、血小板（鸟类中具有高度吞噬能力的细胞）、某些淋巴细胞以及法氏囊和粘液间质内的细胞中发现了B-G抗原。这个项目的目的是试图定义B-G抗原的功能（或功能），根据新发现的B-G分子现在已知的表达位点。B-G抗原一直被认为是鸡的血型抗原。直到最近，人们还认为B-G抗原只在红细胞上表达。现在已知它们在小鸡的各种细胞类型和组织中表达，处于不同的发育阶段。此外，它们已通过DNA测序工作显示与免疫球蛋白基因具有结构相似性。这些新的观察结果导致了一种假设，即B-G抗原可能在鸡的免疫系统中发挥某种作用。本研究的目的是探索这一假设。这项研究的结果有可能揭示鸡的免疫系统是如何运作的。

Significant progress was made recently in defining the structure of the highly polymorphic B-G antigens encoded within the major histocompatibility complex of the chicken. It has been determined that B-G antigens are a family of molecules, divergent members of which are expressed on cells in several different tissues in addition to erythrocytes, including immune system cells. Determination of the sequences of some of the B-G family members has revealed the structural basis of B-G polymorphism, including the presence of hypervariable sequence diversity within an immunoglobulin v-like domain. B-G cytoplasmic tails are made up of heptad repeats of diverse sequence. B-G antigens have been found on the epithelia in the gut, cells in the liver, thrombocytes (highly phagocytic cells in birds), some lymphocytes, and cells within the stroma of the bursa and thumus. The objective of this project is to attempt to define the function (or functions) of the B-G antigens in light of the newly recognized sites where B-G molecules are now known to be expressed. The B-G antigens have long been known as blood group antigens of chickens. Until recently, the B-G antigens were thought to be expressed exclusively on red blood cells. They are now known to be expressed in various cell types and tissues throughout the chick, at various stages of development. Furthermore, they have been shown through DNA sequencing work to have structural resemblance to immunoglobulin genes. These new observations have led to the hypothesis that the B-G antigens may play some role in the chicken immune system. The goal of this study is to explore this hypothesis. The results of this study have the potential to shed new light on how the immune system of the chicken operates.