MT AAB Immunohematology Practice Test

This pattern comes from how Rh antigens are arranged on two chromosomes (the diplotype) and how each chromosome’s RHCE gene determines which C/c and E/e antigens are present. If a red cell shows no D antigen (D negative) but has C and E antigens, and it does not display c or e antigens, the two chromosomes must both carry the CE combination without D.

The only diplotype that fits is dCE/dCE: both chromosomes lack D (d) but carry C and E (CE), so the cells express C and E, but not c or e. That explains why anti-D yields no reaction, anti-C and anti-E yield strong reactions, and anti-c and anti-e yield no reaction.

Other haplotypes would introduce D, or bring in c or e antigens, which would change the serologic reaction pattern and not match the observed results.