In the ABO system of blood groups, if both antigens are present but no antibody, the blood group of the individual would be:

ABO Blood group system $\begin{array}{|c|c|c|c|} \hline \begin{array}{c} \text { Blood } \\ \text { group } \end{array} & \begin{array}{c} \text { Antigen(s) } \\ \text { present on } \\ \text { the red blood } \\ \text { cells } \end{array} & \begin{array}{c} \text { Antibodies } \\ \text { present } \\ \text { in the } \\ \text { serum } \end{array} & \begin{array}{c} \text { Geno- } \\ \text { type(s) } \end{array} \\ \hline \text { A } & \text { A antigen } & \text { Anti-B } & \begin{array}{c} \text { AA or } \\ \text { AO } \end{array} \\ \hline \text { B } & \text { B antigen } & \text { Anti-A } & \begin{array}{c} \mathrm{BB} \text { or } \\ \text { BO } \end{array} \\ \hline \mathrm{AB} & \begin{array}{c} \text { A antigen and } \\ \text { B antigen } \end{array} & \text { None } & \mathrm{AB} \\ \hline \mathrm{O} & \begin{array}{c} \text { B antigen } \end{array} & \begin{array}{c} \text { Anti-A and } \\ \text { Anti-B } \end{array} & \mathrm{OO} \\ \hline \end{array}$ Blood  group ​ A  B ABO​ Antigen(s)  present on  the red blood  cells ​ A antigen  B antigen  A antigen and  B antigen ​ B antigen ​​ Antibodies  present  in the  serum ​ Anti-B  Anti-A  None  Anti-A and  Anti-B ​​ Geno-  type(s) ​ AA or  AO ​BB or  BO ​ABOO​​ Related Theory The ABO blood types were discovered by Karl Landsteiner in 1901.