Participants will undergo apheresis to collect lymphocytes, monocytes, or plasma from the blood. For this procedure, a needle is placed in a vein in the arm. Blood flows from the vein through a tube (catheter) into a machine that spins the blood, separating it into its components. The required cells or plasma are extracted, and the rest of the blood, including the red cells and platelets, is returned to the body through the same needle or through a second needle placed in the other arm.