Klaus Tomasz, Bzowska Monika, Kulesza Małgorzata, Kabat Agnieszka Martyna, Jemioła-Rzemińska Małgorzata, Czaplicki Dominik, Makuch Krzysztof, Jucha Jarosław, Karabasz Alicja, Bereta Joanna
Malopolska Centre of Biotechnology, Jagiellonian University in Kraków, Gronostajowa 7A, 30-387 Kraków, Poland.
Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Gronostajowa 7, 30-387 Kraków, Poland.
Sci Rep. 2016 Aug 3;6:30938. doi: 10.1038/srep30938.
Mouse immunoglobulins M (IgMs) that recognize human blood group antigens induce haemagglutination and are used worldwide for diagnostic blood typing. Contrary to the current belief that IgGs are too small to simultaneously bind antigens on two different erythrocytes, we obtained agglutinating mouse IgG3 that recognized antigen B of the human ABO blood group system. Mouse IgG3 is an intriguing isotype that has the ability to form Fc-dependent oligomers. However, F(ab')2 fragments of the IgG3 were sufficient to agglutinate type B red blood cells; therefore, IgG3-triggered agglutination did not require oligomerization. Molecular modelling indicated that mouse IgG3 has a larger range of Fab arms than other mouse IgG subclasses and that the unique properties of mouse IgG3 are likely due to the structure of its hinge region. With a focus on applications in diagnostics, we compared the stability of IgG3 and two IgMs in formulated blood typing reagents using an accelerated storage approach and differential scanning calorimetry. IgG3 was much more stable than IgMs. Interestingly, the rapid decrease in IgM activity was caused by aggregation of the molecules and a previously unknown posttranslational proteolytic processing of the μ heavy chain. Our data point to mouse IgG3 as a potent diagnostic tool.
识别人类血型抗原的小鼠免疫球蛋白M（IgMs）可诱导血细胞凝集，在全球范围内用于诊断血型。与目前认为IgGs太小而无法同时结合两个不同红细胞上抗原的观点相反，我们获得了识别人类ABO血型系统中抗原B的凝集性小鼠IgG3。小鼠IgG3是一种有趣的同种型，具有形成Fc依赖性寡聚体的能力。然而，IgG3的F(ab')2片段足以凝集B型红细胞；因此，IgG3引发的凝集不需要寡聚化。分子建模表明，小鼠IgG3的Fab臂范围比其他小鼠IgG亚类更大，小鼠IgG3的独特特性可能归因于其铰链区的结构。着眼于诊断应用，我们使用加速储存方法和差示扫描量热法比较了IgG3和两种IgMs在配制血型试剂中的稳定性。IgG3比IgMs稳定得多。有趣的是，IgM活性的快速下降是由分子聚集和μ重链以前未知的翻译后蛋白水解加工引起的。我们的数据表明小鼠IgG3是一种有效的诊断工具。
