Welcome Back to Immunohematology Other Antigen Systems Part II – Kell, Duffy, Kidd, MNSs

Kell System Kx K NH 2 COOH

Kell System  Main antigens are K (Kell) and its allele, k (Cellano).  Antigens are glycoproteins.  K is second only to D in its immunogenicity.  Antigens are not affected by routine enzymes.

Kell System Antibodies  Usually IgG  React best in the Coombs phase (AHG).  Do not show dosage.  Some anti-K antibodies activate complement. Other antibodies in the Kell system do not.

Dosage  An antibody that reacts stronger with a cell that has homozygous expression of an antigen than it does with a cell showing heterozygous antigen expression is said to show dosage.

Kell System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  No  Yes

Duffy System NH 2 COOH Fy a /Fy b

Duffy System  The most common alleles are Fy a and Fy b.  Antigens are glycoproteins.  Antigen frequency varies among the races.  65% of whites are Fy a positive, while only 10% of blacks are Fy a positive.  The most common phenotype in blacks is Fy(a-b-) at 68%. This phenotype in whites is extremely rare.  Destroyed by enzymes.

Duffy System Antibodies  Are IgG.  React best at the AHG phase.  Show dosage.  Some Duffy antibodies activate complement.

Duffy System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  No  Yes

Kidd System Jk a /Jk b NH 2 COOH

Kidd System  The major alleles of the Kidd system are Jk a and Jk b.  Antigens are glycoproteins.  Antigen frequency varies among races.  Jk(a-b-) phenotype extremely rare.  Not very immunogenic.  Enhanced by enzymes.

Kidd System Antibodies  Usually IgG.  Best detected at the AHG phase.  Show dosage.  Noted for ability to activate complement.  Notorious for causing delayed hemolytic transfusion reactions.

Kidd System  Naturally occurring?  HTR?  HDFN?  Clinically significant?  No  Yes

MNSs System COOH NH 2 COOH MN Glycophorin A Glycophorin B Ss

MNSs System  The major antigens of this system are:  M and its allele N  S and its allele s  The most common phenotypes are:  M+N+  S-s+  Antigens can be destroyed by enzymes.

MNSs System Antibodies  Anti-M and -N are usually IgM antibodies.  Many examples of IgG anti-M’s.  Anti-M may react over a wide temperature range (wide thermal amplitude).  Anti-N reacts best in saline (immediate spin).  Anti-S and -s are IgG antibodies.  React best at AHG.  Show dosage.  May activate complement.

MNSs System  Naturally occurring?  M & N yes  S & s usually immune  HTR?  S & s yes  sometimes M, N usually not  HDFN?  S & s yes  M & N no  Clinically significant?  M & N usually not  S & s yes