Dal Porto J, Johansen T E, Catipović B, Parfiit D J, Tuveson D, Gether U, Kozlowski S, Fearon D T, Schneck J P
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21224.
Proc Natl Acad Sci U S A. 1993 Jul 15;90(14):6671-5. doi: 10.1073/pnas.90.14.6671.
Genetically engineered or chemically purified soluble monovalent major histocompatibility complex (MHC) molecules, which have previously been used to study T cells, have not blocked cytotoxic T-cell responses. Here we describe a genetically engineered divalent class I MHC molecule which inhibits lysis of target cells by alloreactive cytotoxic T cells. This protein, H-2Kb/IgG, was generated as a fusion protein between the extracellular domains of a murine class I polypeptide, H-2Kb, and an immunoglobulin heavy chain polypeptide. The chimeric protein has serological and biochemical characteristics of both the MHC and IgG polypeptides. Nanomolar concentrations of H-2Kb/IgG inhibited lysis of H-2Kb-expressing target cells not only by alloreactive H-2Kb-specific T-cell clones but also by alloreactive H-2Kb-specific primary T-cell cultures. A direct binding assay showed high-affinity binding between the H-2Kb/IgG molecule and an H-2Kb-specific alloreactive T-cell clone. Unlabeled H-2Kb/IgG displaced 125I-labeled H-2Kb/IgG from T cells with an IC50 of 1.2 nM.
基因工程改造或化学纯化的可溶性单价主要组织相容性复合体（MHC）分子，此前已用于研究T细胞，但并未阻断细胞毒性T细胞反应。在此，我们描述了一种基因工程改造的二价I类MHC分子，它可抑制同种异体反应性细胞毒性T细胞对靶细胞的裂解作用。这种蛋白质，即H-2Kb/IgG，是作为小鼠I类多肽H-2Kb的胞外结构域与免疫球蛋白重链多肽之间的融合蛋白产生的。该嵌合蛋白具有MHC和IgG多肽的血清学及生化特性。纳摩尔浓度的H-2Kb/IgG不仅抑制同种异体反应性H-2Kb特异性T细胞克隆对表达H-2Kb的靶细胞的裂解，还抑制同种异体反应性H-2Kb特异性原代T细胞培养物对靶细胞的裂解。直接结合试验表明，H-2Kb/IgG分子与H-2Kb特异性同种异体反应性T细胞克隆之间存在高亲和力结合。未标记的H-2Kb/IgG以1.2 nM的半数抑制浓度（IC50）从T细胞中取代125I标记的H-2Kb/IgG。
