Watch NOVA Season 5 Episode 3 Online
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- COUNTRIES: United States of America
- Subtitles: English
It has been known since the turn of the century that there are four human blood groups, based on different red cells and serum characteristics. NOVA looks at the more recent discovery that the different white cell types, as determined by a variety of different molecular markers on the cell surface, open up the possibility of the prevention of disease.
