In the context of blood groups, what does the 'O' group signify?

The 'O' blood group signifies the absence of A and B antigens on the surface of red blood cells. In the ABO blood group system, blood is classified based on the presence or absence of these specific antigens. Group O individuals do not have either A or B antigens, which is why their blood type is considered a universal donor for red blood cells. This absence of antigens allows for group O blood to be transfused into individuals with other blood types without causing an immune response, as there are no A or B antigens to react against.

Understanding the role of antigens is crucial in blood transfusion practices and for ensuring compatibility among different blood types. This knowledge highlights why the 'O' blood group is critically important in medical settings where blood transfusions are necessary.