ABSTRACT
This chapter aims to summarize the data regarding the nature and role of local immunity against bacterial infections and how best this immunity can be elicited. Investigators studying lacrimal, respiratory, gastrointestinal, genitourinary, and mammary secretions all found that IgA was the predominant immunoglobulin. In humans, the IgA to IgG ratio varies, depending on the source of the secretions and results from different laboratories, but in general, the ratio has been found to be between unity and 3:1, as opposed to a serum ratio of 1:5. IgG, IgM, IgE, and IgD have been shown in certain circumstances to be produced locally. Abundant evidence shows that the majority of S-IgA is locally synthesized. S-IgA antibodies to Neisseria gonorrhoeae induced in vaginal secretions after infection tend to disappear promptly, and often without a booster effect following a second infection. Local cell-mediated immunity may be present in the gut in normal animals, as a result of stimulation by viral and bacterial agents, particularly endotoxin.
