Dr. von Haunersches Kinderspital, University of Munich, Lindwurmstr. 4a, D-80337 Munich, Germany.
BMC Pulm Med. 2010 Nov 22;10:59. doi: 10.1186/1471-2466-10-59.
Monomers of the collectin surfactant associated protein-A (SP-A) are arranged in trimers and higher oligomers. The state of oligomerization differs between individuals and likely affects SP-A's functional properties. SP-A can form aggregates together with other SP-A molecules. Here we report and assess a test system for the aggregate forming properties of SP-A in serum and broncho-alveolar lavage samples.
Anti-SP-A antibodies fixed to latex beads bound SP-A at its N-terminal end and allowed the interaction with other SP-A molecules in a given sample by their C-terminal carbohydrate recognition domain (CRD) to agglutinate the beads to aggregates, which were quantified by light microscopy.
SP-A aggregation was dependent on its concentration, the presence of calcium, and was dose-dependently inhibited by mannose. Unaffected by the presence of SP-D no aggregation was observed in absence of SP-A. The more complex the oligomeric structure of SP-A present in a particular sample, the better was its capability to induce aggregation at a given total concentration of SP-A. SP-A in serum agglutinated independently of the pulmonary disease; in contrast SP-A in lung lavage fluid was clearly inferior in patients with chronic bronchitis and particularly with cystic fibrosis compared to controls.
The functional status of SP-A with respect to its aggregating properties in serum and lavage samples can be easily assessed. SP-A in lung lavage fluid in patients with severe neutrophilic bronchitis was inferior.
集胞素相关表面蛋白-A（SP-A）的单体以三聚体和更高的寡聚体形式排列。寡聚状态在个体之间存在差异，可能会影响 SP-A 的功能特性。SP-A 可以与其他 SP-A 分子一起形成聚集体。在这里，我们报告并评估了一种用于检测血清和支气管肺泡灌洗液中 SP-A 形成聚集体特性的测试系统。
固定在乳胶珠上的抗 SP-A 抗体与 SP-A 的 N 端结合，并通过其 C 端碳水化合物识别结构域（CRD）与给定样品中的其他 SP-A 分子相互作用，使珠体聚集在一起，通过光镜对聚集体进行定量。
SP-A 聚集依赖于其浓度、钙离子的存在，并且可以被甘露糖剂量依赖性抑制。在没有 SP-A 的情况下，SP-D 的存在不受影响，没有观察到聚集。在特定样品中存在的 SP-A 寡聚体结构越复杂，在给定的 SP-A 总浓度下诱导聚集的能力就越强。血清中的 SP-A 聚集与肺部疾病无关；相比之下，在慢性支气管炎和囊性纤维化患者的肺灌洗液中，SP-A 的聚集能力明显低于对照组。
可以轻松评估血清和灌洗液中 SP-A 的聚集特性的功能状态。在严重中性粒细胞性支气管炎患者的肺灌洗液中，SP-A 的功能下降。
