Probiotic Ingestion and Isoagglutinin Titers

Background: * Probiotics are oral food supplements containing live bacteria that may be beneficial to a person s digestion or general health. Probiotics are available as tablets, powder, or liquid supplements and are frequently used to supplement yogurt. They are available for purchase without prescription in most supermarkets. * The bacteria in probiotic supplements commonly express sugar substances on their surface. These sugar substances are similar to group A and B blood group sugars, called antigens. These antigens determine a person s blood group. Researchers are studying the effect of probiotic supplements on the amount of blood group antibodies that are present in a person s blood. Objectives: * To determine whether taking oral probiotic supplements increases anti-A and anti-B isoagglutinins (antibodies that cause red blood cells to clump together) in healthy subjects. * To study the frequency of these effects and determine whether there is a dose-response relationship with probiotics and isoagglutinin titers. Eligibility: * Healthy adults, 18 years or older, with type A, B, or O blood. * Female participants need to have undergone menopause or have had a hysterectomy. * Individuals are ineligible if they currently donate platelets; have a history of ulcerative colitis or Crohn s disease; have had major bowel surgery; are pregnant or capable of becoming pregnant; have a bleeding or clotting disorder; have a history of a blood disorder or immune deficiency; have a history of high-risk behaviors for exposure to HIV or hepatitis B or C; have diabetes; have received vaccinations in the past 2 months, with the exception of the flu vaccine; are currently taking immunosuppressive medications; are currently taking antibiotics; or have taken probiotic supplements within the last 12 months. Design: * Researchers will conduct the following tests throughout the 28-week study: * Blood samples will be drawn every 2 weeks to measure the quantity of isoagglutinin titers. * Depending on individual results, continued blood testing may be done every 3 months for 1 year, then every 6 to 12 months for up to 5 years. * Study subjects will take a probiotic supplement at a dose of 1 to 3 caplets per day for 18 consecutive weeks according to the following schedule: * During the first 6-week period, the subject will take one probiotic tablet daily. * During the second 6-week period, the subject will take one probiotic tablet twice daily. * During the third 6-week period, the subject will take one probiotic tablet three times daily. * Control group subjects will be followed in a similar manner but will not take probiotic supplements. * The outcome measure is the percent of probiotic ingestors (the study subjects) versus control group subjects who experience a fourfold or greater rise in isoagglutinin titer. * Study subjects will receive the following financial compensation: $10 per blood sample, for a maximum of $240 if all 24 samples are collected; $100 after completing the first 6-week period; $150 after completing the second 6-week period; and $200 after completing the third 6-week period. * Control subjects will receive $10 per blood sample, for a maximum of $150 if all 15 samples are collected.