LOW-AFFINITY, ANTIBODY-BINDING OF AN ESCHERICHIA COLI-DERIVED COMPONENT

This investigation describes the detection of a component in Escherich ia coli capable of binding a large proportion of human antibody variab le domains including otherwise highly monospecific antibodies induced by an in vivo antibody response. This interaction is of low affinity, but cross-linking of IgG molecules by, e.g. anti-immunoglobulin prepar ations, provides a sufficient degree of multivalency to promote a high avidity interaction. This binding which occurs both with kappa and la mbda light chain-containing antibodies, appears to involve the variabl e region of human antibodies making it a superantigen-like activity. T his is proposed based on the facts that: (i) different human antibodie s of IgG1 isotype appear to bind to different extents suggesting that variable domain differences determine the binding activity; and (ii) a ddition of soluble antigen abrogates the interaction with the E. coli- derived molecule. Future studies of the nature and possible in vivo co nsequences of these interactions are warranted since any superantigen activity associated with this binding might affect the human immune re sponse occurring as a consequence of E. coli infections.