Q38. Anti–B antibodies are present in the serum of ________
(A) Blood group A
(B) Blood group B
(C) Blood group AB
(D) Blood group O
Anti-B antibodies are present in the serum of blood group O.
This is a key concept in the ABO blood group system, where plasma antibodies target antigens absent on an individual’s red blood cells. The correct answer is (D) Blood group O.
Option Analysis
Individuals produce naturally occurring IgM antibodies (anti-A or anti-B) against ABO antigens not present on their own red blood cells, starting around 6 months of age.
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(A) Blood group A: Red blood cells carry A antigens; serum contains anti-B antibodies only.
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(B) Blood group B: Red blood cells carry B antigens; serum contains anti-A antibodies only.
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(C) Blood group AB: Red blood cells carry both A and B antigens; serum lacks anti-A and anti-B antibodies.
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(D) Blood group O: Red blood cells lack A and B antigens (express H antigen); serum contains both anti-A and anti-B antibodies.
ABO Summary Table
| Blood Group | RBC Antigens | Plasma Antibodies |
|---|---|---|
| A | A | Anti-B |
| B | B | Anti-A |
| AB | A and B | None |
| O | None (H) | Anti-A and Anti-B |
Introduction to Anti-B Antibodies Blood Group
Anti-B antibodies blood group refers to the ABO system classification where serum antibodies target B antigens on red blood cells. Individuals lacking B antigens produce Anti-B antibodies naturally, preventing incompatible transfusions. This knowledge is essential for exams like CSIR NET Life Sciences and safe blood matching.
Antigens and Antibodies in Each Blood Group
Red blood cell antigens determine plasma antibodies via Landsteiner’s rule: no antibody matches self-antigens.
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Blood group A has A antigens and Anti-B antibodies.
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Blood group B has B antigens and Anti-A antibodies.
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Blood group AB has both antigens, no antibodies.
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Blood group O has no A/B antigens, both Anti-A and Anti-B antibodies—making Anti-B antibodies blood group O.
Clinical Importance
Anti-B antibodies cause hemolysis in incompatible transfusions, activating complement on B or AB cells. Blood group O acts as universal donor (no antigens) but requires O recipients (both antibodies). Understanding this supports biotechnology applications like plasma therapy.
