Reed J H, Neufing P J, Jackson M W, Clancy R M, Macardle P J, Buyon J P, Gordon T P
Department of Immunology, Allergy and Arthritis, Flinders Medical Centre, Bedford Park, South Australia, Australia.
Clin Exp Immunol. 2007 Apr;148(1):153-60. doi: 10.1111/j.1365-2249.2007.03331.x.
Opsonization of apoptotic cardiocytes by maternal anti-Ro/SSA and anti-La/SSB antibodies contributes to tissue injury in the neonatal lupus syndrome. The objective of the current study was to quantify the surface membrane expression of Ro/La components during different phases of apoptosis and map the Ro/La apotopes (epitopes expressed on apoptotic cells) bound by cognate antibodies. Multi-parameter flow cytometry was used to define early and late apoptotic populations and their respective binding by monospecific anti-Ro and anti-La IgGs. Anti-Ro60 bound specifically to early apoptotic Jurkat cells and remained accessible on the cell surface throughout early and late apoptosis. In contrast, anti-La bound exclusively to late apoptotic cells in experiments controlled for non-specific membrane leakage of IgG. Ro52 was not accessible for antibody binding on either apoptotic population. The immunodominant NH2-terminal and RNA recognition motif (RRM) epitopes of La were expressed as apotopes on late apoptotic cells, confirming recent in vivo findings. An immunodominant internal epitope of Ro60 that contains the RRM, and is recognized by a majority of sera from mothers of children with congenital heart block (CHB) and patients with primary Sjögren's syndrome, was also accessible as an apotope on early apoptotic cells. The distinct temporal expression of the immunodominant Ro60 and La apotopes indicates that these intracellular autoantigens translocate independently to the cell surface, and supports a model in which maternal antibody populations against both Ro60 and La apotopes act in an additive fashion to increase the risk of tissue damage in CHB.
母体抗Ro/SSA和抗La/SSB抗体对凋亡心肌细胞的调理作用导致新生儿狼疮综合征中的组织损伤。本研究的目的是量化凋亡不同阶段Ro/La成分的表面膜表达,并绘制与同源抗体结合的Ro/La凋亡表位(在凋亡细胞上表达的表位)。多参数流式细胞术用于定义早期和晚期凋亡群体以及它们与单特异性抗Ro和抗La IgG的各自结合情况。抗Ro60特异性结合早期凋亡的Jurkat细胞,并在整个早期和晚期凋亡过程中在细胞表面保持可及性。相比之下,在针对IgG非特异性膜渗漏进行控制的实验中,抗La仅与晚期凋亡细胞结合。Ro52在任何一个凋亡群体上都无法与抗体结合。La的免疫显性NH2末端和RNA识别基序(RRM)表位在晚期凋亡细胞上作为凋亡表位表达,证实了最近的体内研究结果。Ro60的一个包含RRM的免疫显性内部表位,被大多数患有先天性心脏传导阻滞(CHB)儿童的母亲和原发性干燥综合征患者的血清所识别,在早期凋亡细胞上也可作为凋亡表位被识别。免疫显性Ro60和La凋亡表位的不同时间表达表明这些细胞内自身抗原独立转运到细胞表面,并支持一种模型,即针对Ro60和La凋亡表位的母体抗体群体以累加方式作用,增加CHB中组织损伤的风险。