Differences in the genotypes and plasma concentrations of the INTERLEUKIN-1 receptor antagonist in black and white South African asthmatics and control subjects

The allelic frequency of a variable tandem repeat (VNTR) polymorphism in intron 2 of the IL-1 Ra gene was studied in black and white patients with asthma as well as control individuals. The plasma IL-1 Ra concentration was also determined in asthmatics and compared to control individuals. The 410-bp allele of the IL-1 Ra was significantly increased in all black subjects (90%) as compared to all white subjects (74%, P<0.0001), while the 240-bp allele was significantly reduced in all black subjects (11%) as compared to all white subjects (27%, P<0.0001). There was no difference in the frequency of the VNTR of the IL-1 Ra between black asthmatics and black controls and between white asthmatics and white controls. The IL-1 Ra levels were significantly increased in black and white patients with severe or moderate asthma as compared to patients with mild asthma. Increased plasma concentrations of the IL-1 Ra was found to be associated with disease severity in all asthmatic patients.

Polymorphisms of the beta chain of the high-affinity immunoglobulin E receptor (Fcepsilon RI-beta) in South African black and white asthmatic and nonasthmatic individuals

We used amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) to document the prevalence of three mutations in the beta chain of the high-affinity IgE receptor (Fcepsilon RI-beta): I181L, V183L, and E237G in a sample of black and white asthmatic and control subjects in South Africa to determine whether these variants contribute to the enhanced IgE responses in these groups and also to determine whether the discrepancy in the prevalence of atopy in these groups could be attributed to these variants, as whites tend to be more atopic than blacks. There was a significant difference in the frequency of I181L between white asthmatics (28%) and white control subjects (3%) (p = 0.00001), and between black control subjects (16%) and white control subjects (p = 0.002); no difference in the frequency of I181L was observed between black asthmatics (22%) and black control subjects (16%). V183L was found in one black asthmatic who was also positive for I181L and E237G. There was a significant difference in the frequency of E237G between black asthmatics (20%) and white asthmatics (12%) (p = 0.05), and between control subjects (20%) and white control subjects (5%) (p = 0.003). E237G was more prevalent in blacks (20%) than in whites (8.5%) (p = 0.001). I181L might predispose to atopy in the white population, but not in the black population. The significantly higher prevalence of E237G in blacks than in whites might explain why blacks tend to have more severe asthma than whites and might offer more insight into the higher asthma mortality rate in the black population as compared with the white population.