Facts about the S and s antigens and antibodies:
- Part of the MNS system.
- S and s antigens are located on the red blood cell surface glycoprotein, glycophorin B.
- Antigens are also expressed in the kidney and epithelium.
- S and s antibodies are capable of causing mild to moderate transfusion reactions as well as HDFN.
- Anti-S can demonstrate at room temperature as well as IAT.
- U is a high-prevalence antigen found in the MNS system.
- S+s-, S-s+, or S+s+ means glycophorin B is present, and thus the U antigen is present.
- The phenotype S-s-U- is typically found in those of African descent. The lack of the U antigen is due to a deletion of the coding region of the GYPB gene.
- Glycophorin B is exploited by the malarial parasite Plasmodium falciparum and just as the GATA mutation causing Fy(a-b-) red cells is linked to malarial resistance, so is the S-s-U- mutation.
- U is not destroyed by enzyme treatment.
- Anti-U has been associated with HTRs and HDFN.
- True U- is extremely rare; approximately 16% of people who are S-s- are a variant with partial U antigens and they can produce Anti-U.
Table 6. S and s Facts.| Ag/Ab | Ag Frequency (White) | Ag Frequency (Black) | Dosage | Enzyme Interaction | Antibody Class | Complement Binding | Clinically Significant |
| S | 55% | 31% | Yes | Variable | IgG | No | Yes |
| s | 89% | 93% | Yes | Variable | IgG | No | Yes |
