Diebel Lawrence N, Liberati David M, Baylor Alfred E, Brown William J, Devlin John
Department of Surgery, Wayne State University, Detroit, MI 48201, USA.
Surgery. 2004 Oct;136(4):937-43. doi: 10.1016/j.surg.2004.06.029.
Secretory immunoglobulin A (SIgA) is the principal immunologic defense of respiratory and other mucosal surfaces in the body. SIgA is relatively stable in mucosal secretions. However, cleavage of SIgA by bacterial proteases might render it immunologically inactive and thus contribute to the development of pneumonia as well as other infections. Bacterial species and infection sites might be important in the expression of bacterial protease activity and serve as the impetus to this study.
Bacterial isolates from respiratory and nonrespiratory sites were incubated with SIgA in vitro. SIgA degradation was determined by size exclusion ultrafiltration and gel electrophoresis.
IgA protease activity was evident in gram-negative but not gram-positive respiratory isolates. Gram-negative isolates from nonrespiratory sources did not exhibit IgA protease activity.
Expression of IgA protease activity might be important in the development and subsequent outcome of gram-negative pneumonia in the patient in the surgical intensive care unit.
分泌型免疫球蛋白A（SIgA）是机体呼吸道及其他黏膜表面主要的免疫防御物质。SIgA在黏膜分泌物中相对稳定。然而，细菌蛋白酶对SIgA的裂解可能使其失去免疫活性，进而导致肺炎及其他感染的发生。细菌种类和感染部位可能对细菌蛋白酶活性的表达具有重要影响，这也是本研究的动因。
将呼吸道及非呼吸道部位分离出的细菌菌株与SIgA进行体外孵育。通过尺寸排阻超滤和凝胶电泳测定SIgA的降解情况。
革兰阴性呼吸道分离菌株中可见IgA蛋白酶活性，而革兰阳性呼吸道分离菌株中未发现。非呼吸道来源的革兰阴性分离菌株未表现出IgA蛋白酶活性。
IgA蛋白酶活性的表达可能对外科重症监护病房患者革兰阴性肺炎的发生及后续转归具有重要意义。
