The scientific name for "self" antigens is major histocompatibility complex (MHC) proteins, and each person bears a unique set. To make matters even more confusing, when these MHC proteins mark the surface of immune cells called leukocytes, the antigens are dubbed human leukocyte antigens (HLAs). Since leukocytes are the cells used for tissue typing, HLAs are what clinicians use to find reasonable matches for their patients. Whether called MHC proteins or HLAs, all are the same thing--"self" antigens. Technicians remove human leukocytes from the blood of potential donors and determine what HLA markers are present.