Elliott W L, Lu S, Nguyen Q, Reisert P S, Sairenji T, Sorli C H, Stille C J, Thomas L J, Humphreys R E
Department of Pharmacology, University of Massachusetts Medical School, Worcester 01605-2397.
Leukemia. 1987 Apr;1(4):395-6.
The p35 protein which is hyperexpressed on hairy leukemic cells was determined to be Ii, the electrophoretically invariant glycoprotein that is associated with class II major histocompatibility complex (Ia) antigens from the time of their synthesis. The principal function of class II MHC antigens is to present to T cell receptors those digested foreign antigenic peptides that probably fold as amphipathic alpha-helices and adsorb to a hydrophobic surface (desetope) on Ia. By a novel strip-of-helix hydrophobicity algorithm we found that the sequence Leu-142 to His-170 in Ii formed a five-cycle, amphipathic, alpha-helix, the highest scoring one among a series of proteins commonly used as experimental antigens. This finding led to the hypothesis that this sequence in Ii bound to the antigen-binding site (desetope) of Ia until release and self-aggregation in the endosome in order that digested foreign peptides could then bind to Ia. Abundant expression of Ii in leukemic cells might be associated with an altered capacity of those cells to present foreign or leukemic antigens to the host's immune system.
在毛细胞白血病细胞上过度表达的p35蛋白被确定为Ii，它是一种电泳不变的糖蛋白，从合成之时起就与II类主要组织相容性复合体（Ia）抗原相关。II类MHC抗原的主要功能是将那些可能折叠成两亲性α螺旋并吸附到Ia上的疏水表面（去表位）的消化后的外来抗原肽呈递给T细胞受体。通过一种新颖的螺旋条带疏水性算法，我们发现Ii中Leu-142至His-170序列形成了一个五圈的两亲性α螺旋，在一系列常用作实验抗原的蛋白质中得分最高。这一发现导致了这样的假设，即Ii中的这个序列与Ia的抗原结合位点（去表位）结合，直到在内体中释放和自我聚集，以便消化后的外来肽随后能够与Ia结合。白血病细胞中Ii的大量表达可能与这些细胞向宿主免疫系统呈递外来或白血病抗原的能力改变有关。
