CD8 Reactivity to Microorganisms in Blood and Breast Milk

Background: When a person is exposed to something that causes an infection, the body sends a type of cell called CD8 T cells to attack it. Those cells are also found in breast milk. Nursing mothers pass these cells to their child, which helps the child fight infections, too. Researchers want to learn more about how CD8 cells work to keep people healthy. Objective: To learn more about how the human body fights off infections. Eligibility: People age 18 years and older who either have an infection, are suspected to have an infection, or recently got a vaccine. The household contacts of these people and people who have not been recently exposed to any infection are also needed. Design: Participants will be screened with a medical and health history and physical exam. They may have blood tests. The first study visit can be the same day as screening. It can be up to 3 months later. For those visits, screening tests will be repeated. At the first visit, participants will have blood collected from an arm vein. Participants who are breastfeeding may provide a small sample of breast milk. They may collect it at home or bring a pumping device to NIH to collect it. NIH can also provide a breast pump. Participants may be contacted for up to 1 year after the first visit to give samples of blood and/or breast milk. Up to 4 additional visits, which will each take about 1 hour, may be scheduled. A personal physician or local lab can collect blood from participants and ship it to NIH. Breast milk cannot be shipped.