These three types of leukocytes are even further divided into more specialized cells, each with their own unique task in the immune system. To learn more details about the immune system, see Additional Resources. How does your immune system know which cells to attack and which cells are part of your own body? Your immune system can recognize cells based on the proteins present on the surface of cells. Viruses, bacteria, and other foreign cells are recognized as being different from your own cells and are attacked by your immune system. Sometimes, one of your own cells changes, or mutates, giving the cell the ability to multiply continuously. Such mutations often are the cause of cancer.
A California domestic partnership is a legal relationship available to all same-sex couples, and to those opposite-sex couples where at least one party is age 62 or older.
A qualified domestic relations order (QDRO) is a court judgment, decree, or order establishing the marital property rights of a spouse, former spouse, child, or dependent of a pension plan participant with respect to certain qualified retirement plans.