New Approach to Help Build Immunity
Apparently, an important part of our immune system and its role in the current pandemic have been largely ignored. This system is known as the mucosal associated lymphoid tissues (MALT). In healthy human adults, the MALT system contributes almost 80% of all immunocytes produced. This system has three main functions: protect the mucous membranes against colonization and invasion by microbes; prevent uptake of ungraded antigens from food, airborne matter and commensal microorganisms; and prevent or reduce the development of potentially harmful immune responses to those antigens if they do reach the body’s interior.1
The MALT system functions independently from the systemic immune system. It is composed of multiple lymphoid compartments, which include the tonsils, adenoids, Peyer patches, and other pockets of lymphoid tissue. Distinct B cell and T cell populations populate the MALT. Once an antigen has been encountered, these cells are produced and then transit through the lymphatic system and enter systemic circulation.
In spite of the fact the COVID-19 pandemic has been with us for more than two years, very little attention has been paid to mucosal immunity in relation to this infection.2 This seems unusual since it has been demonstrated that the virus responsible for the disease initially infects the mucosal surfaces of the respiratory and digestive tracts. It is also of relevance to our profession that the SARS-CoV-2 virus can enter through the mouth, as well as the conjunctival surfaces of the eyes from the aerosols produced during dental procedures.
Furthermore, elevated levels of IgA antibodies against COVID-19 have been found in the nasal fluid, tears and saliva of infected patients. This supports the concept that mucosal IgA in some individuals is produced in response to COVID-19. The response of the MALT system continues at least until the advanced stages of the disease are traceable through the production of circulating antibodies. The MALT response therefore has the potential to be used as an early screening tool, which could allow detection before the virus reaches the lungs and other vital structures. This early warning is possible because it takes six to 10 days after the mucosal immunization event before there is a rise in circulating IgA antibody secreting cells.
The interest in mucosal immunity has increased in the last few years, with more and more studies being funded. Some are focused on developing a test that will not depend on circulating antibodies, as this will allow treatment to be started before COVID-19 disease reaches an advanced stage. There is also great interest in developing a vaccine that works with the MALT system. It is assumed this vaccine would be introduced using a nasal or oral mist, thus reducing the need for injections. This exciting field of research appears to hold promise for the current and future pandemics.
Thomas G. Wilson Jr., DDS
Editor in Chief
- Holmgren J, Czerkinsky C. Mucosal immunity and vaccines. Nat Med. 2005;11(Suppl 4):S45–S53.
- Russell MW, Moldoveanu Z, Ogra PL, Mestecky J. Mucosal immunity in COVID-19: A neglected but critical aspect of SARS-CoV-2 infection. Front Immunol. 2020;11:611337.
From Decisions in Dentistry. February 2022;8(2)4.