8 NCCN Guidelines for Patients ® : Multiple Myeloma, 2019 1 Multiple myeloma Plasma cells You’ve learned that you have or may have multiple myeloma. This chapter explains some basics about this cancer that may help you make treatment decisions. Plasma cells Blood is made of many types of cells, called blood cells. The three main types of blood cells are platelets, red blood cells, and white blood cells. Each type of blood cell has a certain job in the body. Platelets help control bleeding. Red blood cells carry oxygen throughout the body. White blood cells help fight germs and infections in the body. They are part of your body’s disease-fighting system—called the immune system . Most blood cells are made in bone marrow. Bone marrow is the soft, sponge-like tissue found in the center of most bones. See Figure 1. Blood cells are made from special, immature cells called blood stem cells . Blood stem cells can develop into all types of mature blood cells. Many types of white blood cells are made from a blood stem cell. See Figure 2. Types of white blood cells include granulocytes, B cells, and T cells. The different types of white blood cells fight germs in different ways. When germs invade the body, B cells change into plasma cells. In a healthy person, less than 5 out of 100 cells in the bone marrow are plasma cells. Plasma cells make antibodies (also called immunoglobulins). Antibodies are proteins that help your body find and kill germs. Each type of plasma cell makes only one type of antibody. The type of antibody made is meant to attack the specific germ that is causing the infection or illness. There are five types of antibodies or immunoglobulins (IgG, IgA, IgM, IgE, and IgD). Each type has a different role.