Association of MHC class I chain related gene-A microsatellite polymorphism with the susceptibility to T1DM and LADA in Czech adult patients

IL-6 and IL-18 cytokine gene variants of pulmonary tuberculosis patients with co-morbid diabetes mellitus and their household contacts in Hyderabad

PURPOSE

Association of cytokine genes reflects their susceptibility towards infection and disease in household contacts (HHC) of pulmonary tuberculosis (PTB) patients. Hyperglycemia, a common factor in diabetics might influence their risk towards mycobacterium tuberculosis infection and disease development. This study determines the association of IL-6 and IL-18 cytokine gene variants of TB patients with diabetes mellitus (TBDM) and their HHC in Hyderabad.

METHODS

Single nucleotide polymorphisms of IL-6 (-174 G>C and -572 G>C) and IL-18 (-137 G>C and -607 C>A) cytokine genes were genotyped by Amplification Refractory Mutation System and Restriction Fragment Length polymerase chain reaction in total of 705 subjects comprising of TBDM, their HHC, PTB, DM and Healthy controls (HC).

RESULTS

At IL-6 -174G>C variant, GG genotype, G allele in TBDM and TBDM HHC, at -572G>C variant, C allele in TBDM and GG haplotype in TBDM HHC were showing positive association, however DM have not shown any association at IL-6 polymorphic sites. With respect to the IL-18 gene polymorphisms, at -137 G>C variant, GG genotype was positively associated in PTB while at -607 C>A variant positive association was shown with AC genotype in TBDM, their HHC and DM; GACC diplotype in TBDM and GCGC in PTB.

CONCLUSION

Our findings suggest that susceptible combination of IL-6 and IL-18 cytokine genes associated with disease in the HHCs highlight their risk of inclination towards the disease.

The MICA-129Met/Val dimorphism affects plasma membrane expression and shedding of the NKG2D ligand MICA

The MHC class I chain-related molecule A (MICA) is a ligand for the activating natural killer (NK) cell receptor NKG2D. A polymorphism causing a valine to methionine exchange at position 129 affects binding to NKG2D, cytotoxicity, interferon-γ release by NK cells and activation of CD8⁺ T cells. It is known that tumors can escape NKG2D-mediated immune surveillance by proteolytic shedding of MICA. Therefore, we investigated whether this polymorphism affects plasma membrane expression (pmMICA) and shedding of MICA. Expression of pmMICA was higher in a panel of tumor (n = 16, P = 0.0699) and melanoma cell lines (n = 13, P = 0.0429) carrying the MICA-129Val/Val genotype. MICA-129Val homozygous melanoma cell lines released more soluble MICA (sMICA) by shedding (P = 0.0015). MICA-129Met or MICA-129Val isoforms differing only in this amino acid were expressed in the MICA-negative melanoma cell line Malme, and clones with similar pmMICA expression intensity were selected. The MICA-129Met clones released more sMICA (P = 0.0006), and a higher proportion of the MICA-129Met than the MICA-129Val variant was retained in intracellular compartments (P = 0.0199). The MICA-129Met clones also expressed more MICA messenger RNA (P = 0.0047). The latter phenotype was also observed in mouse L cells transfected with the MICA expression constructs (P = 0.0212). In conclusion, the MICA-129Met/Val dimorphism affects the expression density of MICA on the plasma membrane. More of the MICA-129Met variants were retained intracellularly. If expressed at the cell surface, the MICA-129Met isoform was more susceptible to shedding. Both processes appear to limit the cell surface expression of MICA-129Met variants that have a high binding avidity to NKG2D.

Autoimmune diabetes mellitus with adult onset and type 1 diabetes mellitus in children have different genetic predispositions

Type 1 diabetes with manifestation after 35 years of age is defined by CP <200 pmol/L and institution of insulin therapy within 6 months after diagnosis. Latent autoimmune diabetes mellitus in adults (LADA) manifesting after 35 years of age is defined by minimum 6 months after diagnosis without insulin therapy and C peptide (CP) >200 pmol/L and antiGAD > 50 ng/mL. We aimed to find a possible genetic discrimination among different types of autoimmune diabetes. To accomplish this goal, we analyzed DNA samples from 31 LADA patients, 75 patients with adult-onset type 1 diabetes mellitus, 188 type 1 diabetic children, and 153 healthy adult individuals. We studied five genetic loci on chromosomes 6, 11, 4, and 14: HLA DRB1 and DQB1 alleles, major histocompatibility complex (MHC) class I-related gene-A (MIC-A) microsatellite polymorphism, interleukin (IL)-18 single nucleotide polymorphism, the microsatellite polymorphism of nuclear factor kappa B gene (NF-kappaB1), and the single nucleotide polymorphism of a gene for its inhibitor (NF-kappaBIA). HLA-DR3 was detected as the predisposition allele for LADA (OR = 4.94, P < 0.0001). Further we found a statistically significant increase of NF-kappaBIA AA genotype (OR = 2.68, P < 0.01). On the other hand, DRB1*04, which is linked with DQB1*0302, was observed as a risk factor in patients with type 1 diabetes mellitus (T1DM) onset after 35 years of age (OR = 10.47, P < 0.0001 and OR = 9.49, P < 0.0001, respectively). There was also an association with MIC-A5.1 (OR = 2.14, P < 0.01). Statistically significant difference was found in the distribution of IL-18 promoter -607 (C/A) polymorphism between LADA and T1DM in adults (P < 0.01). We conclude that all subgroups of autoimmune diabetes have partly different immunogenetic predisposition.

Killer Cell Immunoglobulin-Like Receptor (KIR) Genes in the Basque Population: Association Study of KIR Gene Contents With Type 1 Diabetes Mellitus

Killer cell immunoglobulin-like receptors (KIR) form a group of regulatory molecules that specifically recognize HLA class I molecules, modulating cytolytic activity of natural killer cells. The number of KIR genes can vary between individuals, significant allelic variations have been described, and KIR genes are organized in a complex and heterogeneous family. In the present study we have performed KIR genotype analysis in the Basque general population. Additionally, we have tested the possible association between KIR gene content (in combination with its HLA ligand) and type 1 diabetes mellitus (T1DM). KIR genotyping was performed using a commercial sequence-specific primer amplification genotyping kit and amino acid position 80 of HLA-C was genotyped by specific amplification and direct sequencing. Haplotypes and genotypes were deduced based on previous studies, and frequencies were compared between disease and control groups. All KIR genes tested were present in Basques and several of these genes (KIR2DS5, KIR3DS1, and KIR2DL2) displayed significant differences from corresponding genes in other Caucasoid populations. In general, Basques present an increase in activating KIR gene frequency and, consequently, the proportion of B haplotypes is higher. Three novel haplotypes were identified in the Basque population. Overall, our results confirm the particular genetic characteristics of the Basque population. No association between KIR gene content and susceptibility to T1DM was observed.