Risk for rheumatic disease in relation to ethnicity and admixture

Table 2 Extent to which known genetic associations can account for west African/European difference in risk for systemic lupus erythematosus

		Risk ratio		Allele frequencies controls
Locus	Alleles	Eur	Afr	Eur	Afr	Population risk ratio*
Loci within the HLA region
HLA-DR [20,21,65]	DRB1*0301 (DRw17)	2^†	1.3^†	0.12	0.14	1.0
	DRB1*0302 (DRw18)
	(HLA-DR2)
	DRB1*1501 (DRw15)	2.4^†	2.7^†	0.13	0.14	1.0
	DRB1*1503 (DRw15)
	(HLA-DR3)
HLA-B [18]	*0801 (B8)	1.8	1.4	0.12	0.03	0.9
C4A [20]	*Q0 (Null)	3.0	3.6	0.1	0.07	0.9
TNF-α [27]	-308A	3.8	2.7	0.12	0.04	0.9
HSP70-2 [25]	8.5-kilobase Pst1	2.1	2.6	0.36	0.61	1.2
Loci outside the HLA region
Mannose-binding protein (54) [28,66]	GAC	1.6	1.4	0.19	0.11	1.0
FCγ RIIa [29]	R131	1.3	1.8	0.51	0.48	1.0

*The population risk ratio has been calculated using the mean of the genotypic risk ratio in Europeans and the genotypic risk ratio in Africans, calculating genotype frequencies assuming Hardy–Weinberg equilibrium. ^†Risk ratios have been calculated by averaging frequencies of HLA-DR2 and HLA-DR3 across studies [21,65]. HLA, human leucocyte antigen; HSP, heat shock protein; TNF, tumour necrosis factor.

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