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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
All adults should have their cholesterol levels checked once every 5 years. During 2009–2010, 69.4% of Americans age 20 and older reported having their cholesterol checked within the last five years.
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.
Approximately 500,000 babies are born each year in the United States to teenage mothers.
Bacteria have been found alive in a lake buried one half mile under ice in Antarctica.