Which Rh antigen is described as an amorph?

Which Rh antigen is described as an amorph?

• A. D
• B. d
• C. C
• D. e

Answer: (B)

In Rh serology, some letters denote a real, detectable antigen, while others describe a form that does not express an antigen at all. The lowercase d denotes absence of the D antigen—an amorph or nonexpressed form at the D locus. Cells carrying the d allele have no D antigen on their surface, so they are Rh(D) negative. The uppercase D, as well as C/c and E/e, are actual antigenic determinants that are expressed on the RBC surface. Because the amorph concept specifically refers to the nonexpression at that locus, the d designation is the one described as amorph.

In Rh serology, some letters denote a real, detectable antigen, while others describe a form that does not express an antigen at all. The lowercase d denotes absence of the D antigen—an amorph or nonexpressed form at the D locus. Cells carrying the d allele have no D antigen on their surface, so they are Rh(D) negative. The uppercase D, as well as C/c and E/e, are actual antigenic determinants that are expressed on the RBC surface. Because the amorph concept specifically refers to the nonexpression at that locus, the d designation is the one described as amorph.