Facts about E and e antigens and antibodies:
- Part of the Rh Blood Group System.
- Less immunogenic than the D antigen. The D antigen has an approximately 80% chance of immunization after each exposure; the E antigen is approximately 1.7%, and the e antigen is approximately 0.5%.
- e is considered a high-incidence antigen and only approximately 2% of donor units will be compatible.
- Antibodies can cause HDFN and HTRs.
- At some institutions, patients with Anti-E are transfused units that are E and c negative due to the likelihood that E negative units are most likely c positive and the chances of forming an Anti-c are higher.
- The probability of immunization after each exposure to the c antigen is approximately 2%.
- The f antigen is found on RBCs of persons who have both the c and e antigen on the same haplotype.
- Anti-f is an antibody directed at c and e antigens when both are present on the same cell or patient's RBCs. These patients are transfused c negative or e negative units.
- RhD-negative people are typically negative for E and positive for e.
Table 2. E and e Facts.| Ag/Ab | Ag Frequency (White) | Ag Frequency (Black) | Dosage | Enzyme Interaction | Antibody Class | Complement Binding | Clinically Significant |
| E | 30% | 21% | Yes | Enhanced by | IgG | No | Yes |
| e | 98% | 99% | Yes | Enhanced by | IgG | No | Yes |
