Cleavage of IgG and IgA in Vitro and in Vivo by the Urinary Tract Pathogen Proteus Mirabilis

Abstract

Pathogenic microorganisms have evolved a number of strategies for avoiding the immune system of the host. For example, Staphylococcus aureus and some Streptococcus spp. express surface proteins which are able to bind immunoglobulins by the Fc region thus eliminating the Fc-mediated effector functions of the immunoglobulins. Some other pathogens secrete proteinases which are able to degrade immunoglobulins (reviewed by Senior et al.¹). These enzymes include a number of highly specific IgA1 proteinases produced by pathogens of mucosal surfaces such as Neisseria meningitidis, Neisseria gonorrhoeae, Haemophilus influenzae and several Streptococcus spp. There is indirect evidence2–4 that these proteinases might be involved directly in the pathogenicity of the microorganisms. A wider range of microorganisms including strains of Proteus spp. and Pseudomonas aeruginosa and Serratia marcescens secrete proteinases of broader specificity which are able, in vitro, to cleave both IgA and IgG and other non-immunoglobulin proteins.