Page 319 - Essential Haematology

Chapter 23 Stem cell transplantation / 305

Father Mother
A1*01:01 A*11:01 A*02:01 A*26:01
B*08:01 B*35:01 B*27:01 B*07:02
DR4 DR1 DR3 DR12
(DRB1*04:02) (DRB1*01:01) (DRB1*03:06) (DRB1*12:05)

Possible
children

A*01:01 A*02:01 A*01:01 A*26:01 A*11:01 A*02:01 A*11:01 A*26:01
B*08:01 B*27:01 B*08:01 B*07:02 B*35:01 B*27:01 B*35:01 B*07:02
DR4 DR3 DR4 DR12 DR1 DR3 DR1 DR12
(DRB1*04:02) (DRB1*03:06) (DRB1*04:02) (DRB1*12:05) (DRB1*01:01) (DRB1*03:06) (DRB1*01:01) (DRB1*12:05)
(a) Child 1 Child 2 Child 3 Child 4

DRB1 DRA1
Haplotype 1
DRB5
Haplotype 2
HLA 14
class II DRB3
Haplotype 3
19
DRB4
Haplotype 4
221 9 2

DRB1β DRα DRB4β DRα

(b)

Figure 23.6 (a) An example of the possible pattern of inheritance of the A, B and DR ( DRB1 ) series alleles of

the human leucocyte antigen (HLA) complex. (b) Molecular genetics of the HLA class II gene complex. There
are four major haplotypes of major histocompatibility complex (MHC) class II genes in the population and each
individual may have up to two (one on each chromosome). The DRA1 gene codes for the DR α protein and the
DRB1 , DRB3 , DRB4 and DRB5 genes encode DR β chains. Expression from the DRB1 gene is higher than from
the other genes. The number of alleles at each gene is shown underneath the gene in italics. Alleles at each
locus have a standard nomenclature (e.g. the alleles at the DRB1 gene are termed DRB1 * 01:01 to DRB1 * 16:08 ).
It is now known that the DR51, DR52 and DR53 antigens, which are defi ned by serological testing, are encoded
from the DRB5 , DRB4 and DRB3 genes, respectively.