Major Histocompatibility Complex Class I Chain-Related A and B (MICA and MICB) Gene, Allele, and Haplotype Associations With Dengue Infections in Ethnic Thais.

BACKGROUND: Major histocompatibility complex class I chain-related (MIC) A and B (MICA and MICB) are polymorphic stress molecules recognized by natural killer cells. This study was performed to analyze MIC gene profiles in hospitalized Thai children with acute dengue illness. METHODS: MIC allele profiles were determined in a discovery cohort of patients with dengue fever or dengue hemorrhagic fever (DHF) (n = 166) and controls (n = 149). A replication cohort of patients with dengue (n = 222) was used to confirm specific MICB associations with disease. RESULTS: MICA*045 and MICB*004 associated with susceptibility to DHF in secondary dengue virus (DENV) infections (odds ratio [OR], 3.22; [95% confidence interval (CI), 1.18-8.84] and 1.99 [1.07-2.13], respectively), and MICB*002 with protection from DHF in secondary DENV infections (OR, 0.41; 95% CI, .21-.68). The protective effect of MICB*002 against secondary DHF was confirmed in the replication cohort (OR, 0.43; 95% CI, .22-.82) and was stronger when MICB*002 is present in individuals also carrying HLA-B*18, B*40, and B*44 alleles which form the B44 supertype of functionally related alleles (0.29, 95% CI, .14-.60). CONCLUSIONS: Given that MICB*002 is a low expresser of soluble proteins, these data indicate that surface expression of MICB*002 with B44 supertype alleles on DENV-infected cells confer a protective advantage in controlling DENV infection using natural killer cells.

Changes in HLA-DR expression, cytokine production and coagulation following endotoxin infusion in healthy human volunteers.

The infusion of a low dose of endotoxin into healthy subjects triggers a complex inflammatory response but the intricacies of which, despite extensive research, are still being unraveled. Nine healthy male volunteers received a dose of 30 Units endotoxin/kg bodyweight as an intravenous bolus. Following endotoxin infusion the concentration of TNF-alpha in their serum rapidly increased within 30 min, peaked after 1-2 h and returned to baseline by 4 h. This corresponded to a similarly rapid increase in anti-inflammatory soluble TNF receptor (sTNFR) levels, which remained elevated for up to 48 h. Increased levels of other cytokines were measured, including IL-6, IL-8, G-CSF, IL-1ra and IL-10. However, these cytokines lagged behind that of TNF-alpha and remained elevated for up to 8 h. Endotoxin injection resulted in complex changes in HLA-DR expression, a marker of monocyte activation state. Initially, following a lag of 2-4 h, HLA-DR expression decreased with a nadir at 8 h, followed by an increase in expression above baseline at 22 h. HLA-DR levels returned to baseline 48 h post-endotoxin challenge. This was in contrast to endotoxin-induced changes in white blood cell (WBC) numbers, which dropped rapidly (at 2-3 h) while HLA-DR levels were stable and then peaked during the nadir in HLA-DR expression (8 h). Furthermore, endotoxin injection caused activation of both fibrinolytic and coagulation pathways. Thus, endotoxin infusion results in complex changes in HLA-DR expression, production of pro- and anti-inflammatory cytokines and activation of coagulation.

High resolution molecular phototyping of MICA and MICB alleles using sequence specific primers.

Major histocompatibility complex (MHC) class I chain-related genes, MICA and MICB, are located centromeric to human leukocyte antigen B (HLA-B) on chromosome 6. In response to stress stimuli, MIC is expressed on epithelial, endothelial and fibroblast cells, but not lymphocytes and has been demonstrated to ligate the natural killer (NK) cell receptor, NKG2D. Nucleotide sequences of MICA and MICB are highly polymorphic and several methods have been established to identify these polymorphisms, including sequence-based typing and sequence-specific oligonucleotide probing. In this study we have developed a high-resolution polymerase chain reaction-sequence-specific primer (PCR-SSP) phototyping scheme that detects all WHO-recognized MICA alleles and all 12 MICB alleles. Our method will also recognize a MICA deletion haplotype and distinguish between MICA alleles with different binding affinities for NKG2D, encoded by a non-synonymous nucleotide substitution in codon 129. Furthermore, our scheme targets almost 90% of the dimorphic codon positions in exons 2, 3, and 4, which result in non-synonymous amino acid changes. This method can be used to determine MIC allele frequencies within different populations, as well as investigate MIC associations in cohorts of patients with autoimmune and infectious diseases and explore the impact of MIC on the survival of solid organ and stem cell transplants.