How is a bone marrow match determined?

HLA type: Every cell in your body has human leukocyte antigens (hlas) on the surface that act like a cell i.D. These allow your immune cells to recognize your cells as part of you and not foreign cells that need to be attacked. The bone marrow donor's hlas should match the patient's hlas as closely as possible so the donor's immune system doesn't attack the patient! hla is determined by a blood test.

From a blood test: Typically a bone marrow or stem cell match is determined from a blood test. The test measures your 'tissue type' by looking at the hla proteins on the surface of your cells. These proteins help your immune system determine what tissues in your body are your own and what are not normal, like bacteria, etc.