Immunoblotting for determination of the antigenic specificities of antibodies to the Mycoplasmatales.

Determination of the nature of antigens towards which specific antibodies are directed has caused great difficulties in studies of the antigenic structure of the Mycoplasmatales. In immunoblotting, polypeptides are separated first by SDS polyacrylamide gel electrophoresis and transferred to cellulose nitrate electrophoretically. The resultant pattern is stained by enzyme-linked staining techniques. This permits direct detection of the antigenic specificities recognized by human and animal immune serum. For example, human convalescent sera from patients with Mycoplasma pneumoniae pneumonia recognize 2 to 7 polypeptides in M. pneumoniae, whereas human sera from patients with postpartum fever from whom Ureaplasma urealyticum has been isolated from the bloodstream detect 15 to 25 polypeptides. A comparison of M. pneumoniae with M. genitalium using rabbit antisera demonstrated that these two organisms show strong cross-reactions, although the organisms can be distinguished. Although certain antigens (epitopes) are destroyed in the procedure, it appears that about two-thirds of the polypeptides retain antigenicity. Immunoblotting provides a powerful means for identifying and subsequently fractionating antigens important to the human immune response.