The <span>ability of leukocytes to move in and out of blood vessels in order to reach sites of inflammation or tissue destruction is known as leukocyte extravasation (also called <em>diapedesis</em><u />).</span>
The factor that is responsible for the phenomenon of the blood group B being almost absent in Native Americans whose ancestors arrived in very small numbers about 10,000 years ago would be called the 'founder effect'.
