Waiting for answer This question has not been answered yet. You can hire a professional tutor to get the answer.
What is HH blood type?
Perhaps you mean the hh blood type. The hh blood type is the rarest blood type which does not express the H antigen present on virtually all RBCs as the building block for other antigens.
The H antigen (genetically HH or Hh) is a surface protein on RBCs that is found in All the major blood groups. The H antigen is the building block for the other surface antigens A and B.
Th hh blood type (also called the Bombay Blood Group because it was first discovered there in 1952), is that in which this protein cannot be expressed.
A person with this blood group would have to receive blood only from another with the same hh blood type, as the blood would react with every other blood group.