Exclusive occurrence of an extracellular protease capable of cleaving the hinge region of human immunoglobulin A1 in strains of Ureaplasma urealyticum.

The purpose of the study was to further investigate the occurrence of a specific immunoglobulin A1 (IgA1) protease among mycoplasmas of various origin. Fifty-two strains representing the genera Mycoplasma, Ureaplasma, Acholeplasma and Spiroplasma were examined. The ability to cause specific cleavage of human IgA1 in the hinge region resulting in intact Fab and Fc fragments was exclusively associated with strains of U. urealyticum. Thus, this trait may be used as a valuable differential characteristic of U. urealyticum. A more pronounced proteolytic activity capable of causing extensive degradation of both human and bovine IgA was demonstrated in the type strain of U. diversum.