α-辅肌动蛋白在IgG型抗双链DNA抗体与系膜细胞结合中的作用

α-actinin is a cross-reactive antigen for the binding of IgG subtype of anti-dsDNA antibodies to mesangial cells

目的探讨α-辅肌动蛋白在介导IgG型抗双链DNA（dsDNA）抗体与系膜细胞结合过程中的作用。方法将体外培养的大鼠系膜细胞株分成4组，其中3组分别与舍有IgG型及IgM型抗dsDNA抗体（Ⅰ组）、含IgM型抗dsDNA抗体（Ⅱ组）以及正常（Ⅲ组）的大鼠血清共同孵育；Ⅳ组预加兔抗鼠α-辅肌动蛋白单抗[并分出少许细胞与辣根过氧化物酶（HRP）-羊抗兔IgG孵育，二氨基联苯胺（DAB）显色]，然后与Ⅰ组同样的血清进行孵育。4组都加入异硫氰酸荧光素（FITC）标记羊抗大鼠IgG单抗，采用流式细胞仪测定细胞表面荧光指数值，同时检测各组系膜细胞的增殖率与活细胞比例。结果从Ⅳ组分出并与HRP-羊抗兔IgG孵育的系膜细胞经DAB显色呈阳性；Ⅰ-Ⅳ组系膜细胞的表面荧光指数分别为1．59±0．22、0.6±0.17、0.66±0.18及0.72±0.16，其中Ⅰ组较Ⅱ-Ⅳ组高（P〈0．05），而各组细胞的增殖水平与活细胞比例差异无统计学意义（p〉0.05）。结论IgG型抗dsDNA抗体可能通过α-辅肌动蛋白与系膜细胞发生交叉结合反应。

Objective To study whether the IgG subtype of anti-double strands DNA （dsDNA） antibodies bind to glomemlar mesangial cells （MCs） by a cross-reactive antigen of α-actinin. Methods The norreal rat MCs cultured in vitro were divided into four groups. Three groups of them were incubated with the rat sera containing IgG and IgM subtypes of anti-dsDNA antibodies （group Ⅰ ）, sera containing only IgM anti-dsDNA antibodies （group Ⅱ ） and normal sera （group Ⅲ） respectively, group Ⅳ was incubated with the same sera of group I after the addition of rabbit anti-α-actinin monoelonal antibodies. Then a few MCs were separated from group IV and incubated with HRP-goat anti-rat IgG and stained with DAB. The goat anti-rat IgG-FITC was used to detect the FITC staining of all groups of MCs by a flow cytometer. Meanwhile their proliferations were measured by thiazoly blue （MTr） assay. Results The part of MCs separated from group IV showed positive staining. The values of fluorescence index （FI） of group Ⅰ to Ⅳ were 1.59±0.22, 0.65±0.17, 0.66±0.18 and 0.72±0.16 respectively. Compared with Group Ⅰ to Ⅲ, the FI of group IV was higher （P〈.0.05）. But there was no significant difference between the proliferation levels and active cell ratios of all groups of MCs （P〉 0.05）. Conclusions The IgG subtype of anti-dsDNA antibodies may bind to MCs by cross-reactive antigen of α-actinin.