The polyspecific antihuman globulin reagent commonly contains antibodies to which combination?

• A. anti-C3d
• B. anti-C3b
• C. anti-IgG
• D. anti-IgG and anti-C3d

Answer: (D)

The key idea is that the polyspecific antihuman globulin (AHG) reagent is designed to detect both antibodies bound to red cells and complement fragments on their surface. It does this by including antibodies against human IgG and against a fragment of complement, typically C3d. This dual specificity allows the direct antiglobulin test to pick up red cells coated with IgG or with complement, increasing sensitivity for immune-mediated reactions. That’s why the common mixture is anti-IgG plus anti-C3d. The other options fall short because anti-C3d alone misses IgG binding, anti-IgG alone would be monospecific, and anti-C3b is not the standard component included in routine polyspecific reagents.