Facts about C and c antigens and antibodies:
- Part of the Rh system.
- Cause of HDFN and HTRs.
- Anti-C is commonly found along with Anti-D.
- Anti-c is commonly found along with Anti-E.
- c antigen is the second most immunogenic of the common Rh antigens after the D antigen in the Rh system.
- The c antigen has a probability of immunization after each exposure of approximately 2%; the C antigen has an approximately 1% chance of immunization.
- People who are RhD-negative are typically negative for the C antigen and positive for the c antigen.
Table 3. C and c Facts.| Ag/Ab | Ag Frequency (White) | Ag Frequency (Black) | Dosage | Enzyme Interaction | Antibody Class | Complement Binding | Clinically Significant |
| C | 70% | 34% | Yes | Enhanced by | IgG | No | Yes |
| c | 80% | 97% | Yes | Enhanced by | IgG | No | Yes |
