If blood of a different or incompatible blood group is transfused into the body, it can trigger a serious immune reaction. This is because the immune system recognizes the transfused blood as foreign and attacks it, leading to a condition called a hemolytic transfusion reaction. Below is a detailed explanation:
Blood Groups and Compatibility
- ABO System: Blood groups (A, B, AB, O) are based on antigens (proteins or sugars) on red blood cells (RBCs).
- Group A: A antigens on RBCs; anti-B antibodies in plasma.
- Group B: B antigens on RBCs; anti-A antibodies in plasma.
- Group AB: Both A and B antigens; no antibodies (universal recipient).
- Group O: No antigens; anti-A and anti-B antibodies (universal donor).
- Rh Factor: Blood is either Rh-positive (has the Rh antigen) or Rh-negative (lacks the Rh antigen).
What Happens in an Incompatible Transfusion?
- Immune System Response:
- If the transfused blood has antigens that your immune system recognizes as foreign, your immune system’s antibodies will attack the transfused RBCs.
- For example, if a person with blood group A receives blood group B, their anti-B antibodies will bind to the B antigens on the transfused blood cells.
- Hemolysis:
- The immune system destroys the transfused red blood cells in a process called hemolysis.
- This releases hemoglobin into the bloodstream, which can be toxic in large amounts.
- Release of Toxins:
- During hemolysis, substances like cytokines and free hemoglobin are released. These can damage organs, especially the kidneys.
- Blood Clotting (Disseminated Intravascular Coagulation, DIC):
- The destruction of RBCs can activate the clotting system, leading to widespread clot formation followed by severe bleeding.
- Shock and Organ Failure:
- Rapid destruction of RBCs can lead to a sudden drop in blood pressure (shock), kidney failure (due to clogged kidney tubules), and multi-organ failure.
Symptoms of a Hemolytic Reaction
- Fever and chills
- Severe back or flank pain
- Dark or red urine (due to hemoglobin release)
- Low blood pressure
- Rapid heartbeat
- Difficulty breathing
- Nausea and vomiting
- Jaundice (yellowing of the skin and eyes)
Long-Term Consequences
- Kidney damage: Hemoglobin from destroyed RBCs can clog the kidneys, leading to acute kidney injury.
- Severe anemia: Due to the loss of RBCs.
- Death: If untreated, severe reactions can be fatal.
Prevention
- Blood Typing and Crossmatching: Before transfusion, the patient’s blood is tested to determine the blood group and Rh factor. A crossmatch test ensures compatibility between the donor’s and recipient’s blood.
- Use of Universal Donors: O-negative blood (no A/B antigens, no Rh antigen) can be used in emergencies for any blood group.
Treatment if Reaction Occurs
- Stop the Transfusion: Immediately halt the transfusion at the first sign of a reaction.
- Supportive Care: Administer fluids to support blood pressure and protect the kidneys. Diuretics may help flush out free hemoglobin.
- Medication: Steroids or antihistamines can reduce the immune response.
- Dialysis: In severe cases, dialysis may be required to support kidney function.
In short, receiving incompatible blood can be life-threatening, but rigorous screening and testing make such events rare in modern medical practice.
