In warm autoimmune hemolytic anemia, the IgG antibody is formed against p antigen on the surface of RBC. This is true.
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warm autoimmune hemolytic anemia IgG antibody antigen target RBC
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This statement is false.
In warm autoimmune hemolytic anemia (WAIHA), the IgG autoantibody is directed against antigens on the Rh blood group system (most commonly Rh antigens, particularly the e antigen or other Rh determinants) — not the p antigen.
Here is the correct breakdown:
| Type of AIHA | Antibody | Thermal Amplitude | Target Antigen |
|---|---|---|---|
| Warm AIHA | IgG | 37°C (body temp) | Rh system antigens (e.g., e, D, or "pan-Rh") |
| Cold agglutinin disease | IgM | <37°C (cold) | I antigen (rarely i) |
| Paroxysmal Cold Hemoglobinuria (PCH) | IgG (Donath-Landsteiner) | Biphasic | P antigen |
The p antigen (P blood group system) is the target in Paroxysmal Cold Hemoglobinuria (PCH), not warm AIHA. In PCH, the Donath-Landsteiner antibody (an IgG) binds to the P antigen in cold temperatures and causes complement-mediated lysis upon rewarming — making it a cold-reacting IgG despite being classified separately from cold agglutinin disease.
So the key correction: P antigen → PCH (Donath-Landsteiner antibody), not warm AIHA.
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