Leptospira multiplies persistently in the lumen of the kidney tubules of rats and is shed in the urine and remains infectious. Induction of Ineffective Antibody Many types of antibody are formed against a given Ag, and some bacterial components may display various antigenic determinants. If Abs formed against a bacterial Ag are of low avidity, or if they are directed against unimportant antigenic determinants, they may have only weak antibacterial action. Abs might even aid a pathogen by combining with a surface Ag and blocking the attachment of any functional Abs that might be present. Increased susceptibility to reinfection is highly correlated with the presence of circulating rmp antibodies.
Some bacteria can liberate antigenic surface components in a soluble form into the tissue fluids.
Streptococcus pneumoniae and Neisseria meningitidis are known to release capsular polysaccharides during growth in tissues. They are found in the serum of patients with pneumococcal pneumonia and in the cerebrospinal fluid of patients with meningitis. Protein A, produced by S. aureus may remain bound to the staphylococcal cell surface or it may be released in a soluble form. There are probably several ways that pathogens interfere with the antibacterial action of antibody molecules. Some pathogens produce enzymes that destroy antibodies.