• Ureaplasma;
  • IgA;
  • IgA1 protease;
  • mucosal immunity

Thirteen serovars of Ureaplasma urealyticum were analyzed for the ability to cleave human IgA. Strains of all of the serovars tested cleaved IgA1 in the hinge region of the α-chain, resulting in intact Fc and monomeric Fab fragments. IgA1 protease activity was also observed in concentrated cell-free extracts of spent cultivation medium, indicating that the IgA1 protease was excreted into the medium during growth of the micro-organisms. Five clinical isolates of U. urealyticum obtained from urine, cervix, vagina, amniotic fluid, and synovial fluid were positive for IgA1 protease activity. No proteolytic activity was observed against human IgA2, IgG, or IgM. Strains of Mycoplasma fermentans, M. salivarium and seven serovars of M. hominis were negative for IgA1 protease activity.