Chapter 7: Other Blood Group Systems, Human, Leukocyte Antigens, and PLT Antigens

Kell Blood Group System

- K and k antigens are antithetical

- K (K1) antigen is very immunogenic in stimulating antibody production

Kell Antigens

Destroyed by Dithiothreitol (DTT)

Kell Antibodies

- IgG

- RBC stimulated (transfusion or pregnancy)

- Agglutinate best in IAT

- Associated with HTRs and HDFN

- Anti-K (K1) is the most common

Lack of Kx Antigens

leads to RBC abnormalities/acanthocytes (McLeod phenotype)

McLeod Syndrome

Associated with chronic granulomatous disease

Duffy

- Destroyed by enzymes

- Fya and Fyb: codominant alleles, most important for transfusion purposes

Duffy Antibodies

- IgG

- stimulated by transfusion or pregnancy but not a common cause of HDFN

- doesn't react with enzyme treated RBCs-Antigens are sensitive to ficin and papain

- Show dosage

Duffy System and Malaria

- Most African Americans are Fy(a-b-)

- Certain malarial parasites (Plasmodium knowlesi and Plasmodium vivax) will not invade Fy(a-) and Fy(b-) negative cells

Kidd System

- show dosage

- Enhanced by enzymes (ficin and pipain)

Kidd Antibodies

- Clinically significant

- Implicated in HTRs and HDFN

- Common cause of delayed HTRs

- Detection is aided by enzymes, LISS, and PEG

- Titer drops quickly (antibodies can go undetected)

anti-Lua

IgM and few are IgG, not clinically significant

anti-Lub

IgG, associated with transfusion reactions (clinically significant)

Lewis

- Lewis antigens are found in secretions (glycoproteins) and plasma (glycolipids)

- Glycolipids absorb onto RBC membrane

Lewis Antigens

- Lea and Leb are not separate alleles

- Lewis system depends on Hh, Se, and Le genes

- Le, H, and Se genes must all be inherited to convert Lea to Leb Le (a-,b+)

Lewis Antibodies

IgM, not clinically significant

I Antibodies

Usually autoantibody (autoanti-I), reactions are avoided by prewarming

Autoanti-I

mycoplasma pneumoniae

Anti-i

infectious mononucleosis

P1PK

P1 antigen is detected in plasma and hydatid cyst fluid

Autoanti-P

- Cold paroxysmal hemoglobinuria

- IgG (Donath-Landsteiner antibody); a biphasic hemolysin that binds with P1 or P2 cells at low temperatures before the complement is activated on warmer temp

M and N

- coded by glycophorin A

- show dosage: homozygous inheritance enhances agglutination [(M+N-) or (M-N+)]

S, s, and U

- Coded by glycophorin B

-U antigen: Located near membrane, Present when S or s is inherited

-Absence of glycophorin B (GPB) would result in S-s-U-

Rare IgM

N-like antibodies found in dialysis patients from formaldehyde-sterilized instruments

HLAs

Antibodies can cause refractoriness and transfusion reactions

MHC Genes

Class I and Class II

Class I

plts, leukocytes, nucleated cells

Class II

macrophages, dendritic cells, B cells (APC)

HPC Transplants

Allelic level HLA matching prevents rejection and GVH disease

PLT Antigens

- Common PLT antibody targets HPA-1a

- Antibodies to PLTs may cause PTP

-Can cause refractoriness for platelet transfusions (PTP)