Genetic polymorphisms in adaptive immunity genes and childhood acute lymphoblastic leukemia

BACKGROUND

Childhood acute lymphoblastic leukemia (ALL) has been hypothesized to have an infection- and immune-related etiology. The lack of immune priming in early childhood may result in abnormal immune responses to infections later in life and increase ALL risk.

METHODS

The current analyses examined the association between childhood ALL and 208 single-nucleotide polymorphisms (SNP) of 29 adaptive immune function genes among 377 ALL cases and 448 healthy controls. Single SNPs were analyzed with a log-additive approach using logistic regression models adjusted for sex, age, Hispanic ethnicity, and race. Sliding window haplotype analyses were done with haplotypes consisting of 2 to 6 SNPs.

RESULTS

Of the 208 SNPs, only rs583911 of IL12A, which encodes a critical modulator of T-cell development, remained significant after accounting for multiple testing (odds ratio for each copy of the variant G allele, 1.52; 95% confidence interval, 1.25-1.85; P = 2.9 x 10(-5)). This increased risk was stronger among firstborn children of all ethnicities and among non-Hispanic children with less day care attendance, consistent with the hypothesis about the role of early immune modulation in the development of childhood ALL. Haplotype analyses identified additional regions of CD28, FCGR2, GATA3, IL2RA, STAT4, and STAT6 associated with childhood ALL.

CONCLUSION

Polymorphisms of genes on the adaptive immunity pathway are associated with childhood ALL risk.

IMPACT

Results of this study support an immune-related etiology of childhood ALL. Further confirmation is required to detect functional variants in the significant genomic regions identified in this study, in particular for IL12A.

Analysis of maternal-offspring HLA compatibility, parent-of-origin effects, and noninherited maternal antigen effects for HLA-DRB1 in systemic lupus erythematosus

OBJECTIVE

Genetic susceptibility to systemic lupus erythematosus (SLE) is well established, with the HLA class II DRB1 and DQB1 loci demonstrating the strongest association. However, HLA may also influence SLE through novel biologic mechanisms in addition to genetic transmission of risk alleles. Evidence for increased maternal-offspring HLA class II compatibility in SLE and differences in maternal versus paternal transmission rates (parent-of-origin effects) and nontransmission rates (noninherited maternal antigen [NIMA] effects) in other autoimmune diseases have been reported. Thus, we investigated maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 in SLE.

METHODS

The cohort comprised 707 SLE families and 188 independent healthy maternal-offspring pairs (total of 2,497 individuals). Family-based association tests were conducted to compare transmitted versus nontransmitted alleles (transmission disequilibrium test) and both maternally versus paternally transmitted (parent-of-origin) and nontransmitted alleles (using the chi-square test of heterogeneity). Analyses were stratified according to the sex of the offspring. Maternally affected offspring DRB1 compatibility in SLE families was compared with paternally affected offspring compatibility and with independent control maternal-offspring pairs (using Fisher's test) and was restricted to male and nulligravid female offspring with SLE.

RESULTS

As expected, DRB1 was associated with SLE (P < 1 x 10(-4)). However, mothers of children with SLE had similar transmission and nontransmission frequencies for DRB1 alleles when compared with fathers, including those for the known SLE risk alleles HLA-DRB1*0301, *1501, and *0801. No association between maternal-offspring compatibility and SLE was observed.

CONCLUSION

Maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 are unlikely to play a role in SLE.

High-density SNP screening of the major histocompatibility complex in systemic lupus erythematosus demonstrates strong evidence for independent susceptibility regions

A substantial genetic contribution to systemic lupus erythematosus (SLE) risk is conferred by major histocompatibility complex (MHC) gene(s) on chromosome 6p21. Previous studies in SLE have lacked statistical power and genetic resolution to fully define MHC influences. We characterized 1,610 Caucasian SLE cases and 1,470 parents for 1,974 MHC SNPs, the highly polymorphic HLA-DRB1 locus, and a panel of ancestry informative markers. Single-marker analyses revealed strong signals for SNPs within several MHC regions, as well as with HLA-DRB1 (global p = 9.99×10⁻¹⁶). The most strongly associated DRB1 alleles were: *0301 (odds ratio, OR = 2.21, p = 2.53×10⁻¹²), *1401 (OR = 0.50, p = 0.0002), and *1501 (OR = 1.39, p = 0.0032). The MHC region SNP demonstrating the strongest evidence of association with SLE was rs3117103, with OR = 2.44 and p = 2.80×10⁻¹³. Conditional haplotype and stepwise logistic regression analyses identified strong evidence for association between SLE and the extended class I, class I, class III, class II, and the extended class II MHC regions. Sequential removal of SLE–associated DRB1 haplotypes revealed independent effects due to variation within OR2H2 (extended class I, rs362521, p = 0.006), CREBL1 (class III, rs8283, p = 0.01), and DQB2 (class II, rs7769979, p = 0.003, and rs10947345, p = 0.0004). Further, conditional haplotype analyses demonstrated that variation within MICB (class I, rs3828903, p = 0.006) also contributes to SLE risk independent of HLA-DRB1*0301. Our results for the first time delineate with high resolution several MHC regions with independent contributions to SLE risk. We provide a list of candidate variants based on biologic and functional considerations that may be causally related to SLE risk and warrant further investigation.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and involvement of multiple organ systems. Although the cause of SLE remains unknown, several lines of evidence underscore the importance of genetic factors. As is true for most autoimmune diseases, a substantial genetic contribution to disease risk is conferred by major histocompatibility complex (MHC) gene(s) on chromosome 6. This region of the genome contains a large number of genes that participate in the immune response. However, the full contribution of this genomic region to SLE risk has not yet been defined. In the current study we characterize a large number of SLE patients and family members for approximately 2,000 MHC region variants to identify the specific genes that influence disease risk. Our results, for the first time, implicate four different MHC regions in SLE risk. We provide a list of candidate variants based on biologic and functional considerations that may be causally related to SLE risk and warrant further investigation.

Validation of a simple, manual urinary iodine method for estimating the prevalence of iodine-deficiency disorders, and interlaboratory comparison with other methods

The measurement of urinary iodine in population-based surveys provides a biological indicator of the severity of iodine-deficiency disorders. We describe the steps performed to validate a simple, inexpensive, manual urinary iodine acid digestion method, and compare the results using this method with those of other urinary iodine methods. Initially, basic performance characteristics were evaluated: the average recovery of added iodine was 100.4 +/- 8.7% (mean +/- SD), within-assay precision (CV) over the assay range 0-0.95 mumol/L (0-12 micrograms/dL) was < 6%, between-assay precision over the same range was < 12%, and assay sensitivity was 0.05 mumol/L (0.6 microgram/dL). There were no apparent effects on the method by thiocyanate, a known interfering substance. In a comparison with five other methods performed in four different laboratories, samples were collected to test the method performance over a wide range of urinary iodine values (0.04-3.7 mumol/L, or 0.5-47 micrograms/dL). There was a high correlation between all methods and the interpretation of the results was consistent. We conclude that the simple, manual acid digestion method is suitable for urinary iodine analysis.

Iron deficiency anemia in children

Even when simple iron deficiency is strongly suspected, the child with severe anemia deserves a careful and thorough work-up before treatment is begun. Many other possible causes of anemia need to be excluded. No one test specifically identifies iron deficiency, but the combined use of several tests of iron status can establish iron deficiency with certainty. Hemoglobin level, mean corpuscular volume, serum iron, total iron binding capacity, free erythrocyte porphyrin and serum ferritin are the important studies.