If a person has antigens A and B in R.B.C. Which antibodies will be present in…
2013
If a person has antigens A and B in R.B.C. Which antibodies will be present in the serum?
- A.
Antibody A
- B.
Antibody B
- C.
No Antibody
- D.
Both Antibody A & B
Show answer & explanation
Correct answer: C
By Landsteiner's Law, a person's blood serum naturally develops antibodies only against the ABO antigens that are absent from their own red blood cell surface — the immune system does not produce an antibody against any antigen it recognises as self, since that would trigger destruction of the person's own cells.
In this question, the red blood cells carry both antigen A and antigen B, so neither is an absent (non-self) antigen for this person's immune system to react against; consequently, it does not raise anti-A or anti-B antibodies. This antigen combination is Blood Group AB; AB serum is free of anti-A and anti-B antibodies — clinically termed the 'universal recipient' because it carries no ABO antibody that would attack a transfused A, B, AB, or O red cell.
The complete ABO pattern below confirms this is the only self-consistent combination:
Blood Group | Antigen(s) on Red Blood Cell | Antibody(ies) in Serum |
|---|---|---|
A | Antigen A | Anti-B |
B | Antigen B | Anti-A |
AB | Antigen A and Antigen B | None |
O | None | Anti-A and Anti-B |
Only the AB row carries both antigens with zero circulating antibodies — matching the person described, so the serum contains no antibody.