This research study goal is to analyze the plasma and the cells that make up part of the immune system. These cells, called white cells or leukocytes, are present in blood. We want to learn how these cells work to prevent infection and how they respond after an infection occurs. We also want to study certain molecules present on the plasma, on or in these cells, and the genetic material that allows these molecules to be made. These molecules may influence why one person will develop an infection and another will not, or why one person develops severe symptoms of a disease while others remain without symptoms. This study may increase our understanding of a variety of diseases including infections such as HIV, allergic diseases such as asthma, joint diseases such as rheumatoid arthritis, certain cancers, and the rejection process that sometimes occurs after transplantation of an organ.