Participants needed for studies involving IMMUNE RESPONSES AND AGING at Stanford University/VA Palo Alto Background: The immune system is critical to fight infections and cancer. With age, the production of immune cells declines and the pool of immune cells get older and dysfunctional. These changes are already apparent in middle-aged individuals and lead to increased risk for cancer and infections and diminished vaccine responses. It is, therefore, important to identify these changes and to find means to prevent or reverse them. Purpose of Study: The goal of this study is to identify changes in the immune system that occur with aging. Procedures: ● Volunteers must be 20-85 years old and in good health. ● All participants will have a single blood draw, taking less than 0.5 hr. Study participants will receive $30 for time, inconvenience, and travel. For general information about participant rights, contact 1-866-680-2906. For more information or study enrollment, please email us at the above address. In your email, please provide your name and a telephone number for us to contact you.