Immunohistochemical localization and bacteriostatic properties of an iron-binding protein from bronchial mucus.

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Abstract
Lactoferrin, an iron-binding protein present in bronchial secretions, milk, and saliva but absent from the serum, was investigated with regard to its site of origin in the bronchial tree. [Human] frozen biopsy sections were incubated with f luorescein-labelled antiserum specifically reacting with lactoferrin. This protein was present in all bronchial glands. Both serous and mucous cells, especially the former, appeared to be involved in the production of lactoferrin. Purified lactoferrin exhibited a bacteriostatic activity against Staphylococous albus but not against S. aureus. This effect is due to the iron-binding properties of the protein, since it could be abolished by supplying an excess of ionized iron to the medium.