These are derived either from the circulation or are produced by the mucosa. Some compounds, such as lactoferrin, are present only in nasal secretions. Many proteins are involved in the immunological responses of the nose. A number of other plasma proteins and macromolecules are present because of capillary leakage.
Lactoferrin is produced by the glandular epithelium, mainly the serous cells. Its action is to bind divalent metalions – like transferrin in the circulation; transferrin is not found in secretions in any quantity. They both bind two divalent metal ions, particularly iron, and have amolecular weight of 76-77,000 daltons. By removing heavy metal ions, it prevents growth of certain bacteria, particularly staphylococcus and pseudomonas.
Lysozymes come from the serous glands and tears. They are also produced from leukocytes and macrophages, which are found in nasal secretions and mucosa. Their actions are nonspecific and act only on bacteria without capsules.
A number of different antiproteases have been demonstrated and they increase with infection; their role remains uncertain. They include Alpha-antitrypsin, Alpha 1-antichymotrypsin, Alpha 2 macroglobulin and other antiproteases produced by leukocytes.
All components have been identified. C3 is produced by the liver and locally by macrophages. It is activated by both nonspecific and specific immunological responses through the alternative and classical pathways. Its functions include the lysis of microorganisms and enhancing neutrophil function as well as leukotaxis.
Phospholipids and triglycerides are present; their exact function is unknown.
IONS AND WATER
Na + and Cl – are hyperosmolar in mucus. Evaporation may account for some of the hyperosmolarity but active ion transport also exists. This occurs mainly within the serous glands, which produce the major proportion of the fluid in nasal secretions.
All classes of immunoglobulins have been found in nasal secretions. Two immunoglobulins involved with mucosa defense, IgA2 and IgE, are present in greater quantities than serum. IgA accounts for 50 percent of the total protein content.