New evidence explains poor infant immune response to certain vaccines, says MU ...( COLUMBIA Mo. For years researchers ...)

COLUMBIA, Mo. For years, researchers and physicians have known that infants' immune systems do not respond well to certain vaccines, thus the need for additional boosters as children develop. Now, in a new study from the University of Missouri, one researcher has found an explanation for that poor response. In the study, the MU scientist found evidence that the immune systems of newborns might require some time after birth to mature to a point where the benefits of vaccines can be fully realized.

Habib Zaghouani, a professor of molecular microbiology and immunology and child health at the MU School of Medicine, recently found that a slowly maturing component of the immune system might explain why newborns contract infections easily. In his work, Zaghouani studied newborn mice and how their immune systems reacted when they were repeatedly exposed to an antigen that simulates a virus.

Zaghouani found that while the antigen would prompt a response of the immune system, it was not the expected response. In the adult immune system, two major types of cells, known as T-helper 1 (Th-1) and T-helper 2 (Th-2) cells, are instrumental in the development of an effective immune response. Typically, Th-1 cells respond when dangerous microbes enter the body. The Th-1 cells then work to help destroy the foreign microbes. When an antigen from a vaccine enters a body with a mature immune system, Th-1 cells respond and, after destroying the invader, the Th-1 cells "remember" how to fight the antigen for future battles. Th-2 cells typically develop when the body is exposed to allergens. The responses of Th-2 cells are usually strong and manifest in the form of allergic reactions.

When Zaghouani gave the newborn mice an antigen shortly after birth, he noticed the presence of both Th-1 and Th-2 cells. However, when he gave the antigen a second time, he noticed an abundance of Th-2 cells that responded to the antigen instead of Th-1 cells. Zaghouani was s
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