Yael:I  just  read  about  an  exciting  technique.Researchers  found  a  way  to  convert  types  A  and  B  blood  into  type  O  blood--the  type  that  can  be  transfused  into  any  patient.This  advance  could  help  avoid  blood  shortages  in  the  future.
Don:Wow,that  is  exciting.But  what  makes  type  O  blood  so  special?
Y:Blood  types  result  from  different  carbohydrates,called  antigens,on  the  surface  of  human  blood  cells.Your  blood "type"denotes  the  kinds  of  antigens  you  have  on  the  surface  of  your  cells.People  with  type  A  blood  have  A  antigens;those  with  type  B  have  B  antigens.If  you  have  both  kinds  of  antigens,you're  type  AB;if  you  have  neither  one,you're  type  O.
Your  immune  system  recognizes  the  antigens  on  your  blood  as "self",but  attack  cells  with "foreign"antigens.So  if  you  ever  need  a  blood  transfusion,it's  important  that  you  only  receive  blood  compatible  with  your  own  type.
D:I  see.So  if  a  type  A  person  receives  type  B  or  AB  blood,her  immune  system  will  see  the  B-antigens  as  foreign,and  attack  the  donor  blood  cells?
Y:Exactly.But  type  O  is  called  the "universal  donor"since  it  doesn't  have  any  antigens  that  would  set  off  the  body's  defense  system.
A  team  of  Danish  scientists  has  identified  enzymes  that  remove  the  A  and  B  antigens  from  blood  cells.The  enzymes,which  were  extracted  from  a  bacteria  and  a  fungus,essentially  change  any  donated  blood  into  type  O.
Clinical  trials  are  underway  to  test  whether  the  treated  blood  is  safe  and  effective.If  so,the  technology  could  help  save  lives,since  type  O  blood  is  such  a  precious  commodity