Recent advances in real-time mass spectrometry detection of bacteria, p 929C954. the role of ECA in the host immune response, Dutogliptin as well as its potential roles in host-pathogen interaction. Furthermore, we explore recent work that offers insights into the cellular function of ECA. This review provides a glimpse of the biological significance of this enigmatic molecule. is a bacterial order that is defined in part by the presence of an antigen known as enterobacterial common antigen (ECA) (26). ECA, a carbohydrate antigen, is located in the outer leaflet of the OM and in the periplasm (27,C30). Although express various antigens (e.g., K, O, and H) (31, 32), ECA is unique in that it is restricted to one order and in which it is invariant (Fig.?1A) allowing cross-reactivity among the members of (33). Open in a separate window FIG?1 The structure of ECA. (A) The structure of the repeating unit (R) of ECA is made up of amino sugars (G, causing urinary tract infections and observing the reaction between rabbit antisera generated Dutogliptin against the strains and 102 homologous and heterologous strains. The authors used a standard procedure (passive hemagglutination) to detect O-antigen found in the LPS of the (33). While carrying out these experiments, they realized there was a cross-reacting specificity between the antisera and many strains of O14 sera reacted with a remarkable range of strains: anti-O14 serum had antibodies recognizing an antigen common to various strains. However, this antigen was not the LPS-attached O-antigen that Kunin and colleagues had been investigating (33). Furthermore, this cross-reacting antigen was also observed in most other enteric bacteria (33, 34). The antigen was, therefore, named enterobacterial common antigen (ECA) (35). After the discovery of ECA, research was conducted to ascertain the dissemination of the new antigen among species, eventually aided by a monoclonal ECA antibody that enhanced ECA detection (36). ECA is present in wild-type strains of and absent in both other Gram-negative bacteria and Gram-positive bacteria (Table?1). More studies need to be carried out on the unusual presence of enterobacterial common antigen in 209A, as it is not present in the other strains belonging to the same species (37) and may be the result of horizontal gene transfer. Few exceptions to the ubiquitous expression of ECA Nkx1-2 in exist. These species, which appear to have lost ECA expression, are the endosymbiotic members of Arsenophonus lipoptenaeFukatsuia209A(40,C42). However, the importance of common antigens has often been overlooked. In recent times, the study of these antigens has increased given their potential significance in vaccine development, determination of phylogeny, and diagnosis. Furthermore, the invariance of common antigens suggests that they have important functions that do not allow for variability. ECA is a perfect example of an antigen that has undergone a recent resurgence of research despite its discovery many years ago. In this review, we explore the history of ECA, its conversation with the immune system, its isolation and biosynthesis, and finally its biological significance. THE IMMUNOGENICITY OF ECA Interactions of ECA with the immune response. ECA has a complex interaction with the immune response. Initial studies elucidated that, while the antigen occurred across O14 (33, 43). Thus, Dutogliptin all strains possessed antigenic ECA but very few possessed immunogenic ECA. The variance in immunogenicity of the strains analyzed could not be accounted for by differences in the amounts of ECA expressed (35, 44, 45). Therefore, something else must differentiate these types of ECAs. The elucidation of this difference came by separating ECA extracts with ethanol,.