Adhesion inhibition by antibodies.

The barrier function of the mucous membranes is exerted through unspecific defense mechanisms like mechanic washing and by specific immunity. Antibodies in secretion do not mainly act through bactericidal mechanisms, but rather by binding to antigens, neutralizing, agglutinating and immobilizing them. The net result will be a decreased chance for bacteria to reach and bind to host epithelial cells. Antibodies directed against bacterial adhesions will specifically interfere with the adhesion process. On E. coli causing urinary tract infection, the surface structures responsible for adhesion may be pili or fimbriae. Evidence is accumulating that different parts of the pilus are involved in attachment and immune response. Thus, poor cross-reactivity was found between E. coli 3660 and 3048 pili, although they react with the same P blood group receptor antigens. Little cross-inhibition of adhesion was found, although each anti-pili antibody totally blocked attachment of the homologous strain. In children with acute pyelonephritis, an antibody response to pili of the infecting E. coli strain was found in serum and urine. No consistent antibody response to MS pili was found in 25 children tested.