Polymorphism of the 5' flanking region of the IL-12 receptor beta2 gene partially determines the clinical types of leprosy through impaired transcriptional activity.

BACKGROUND: Individual differences in T cell responsiveness to interleukin 12 (IL-12), resulting from inherited factors, may be responsible for differences in the intensity of cell mediated immune (CMI) responses in patients with leprosy, a disease with a wide clinical spectrum. AIM: Polymorphisms in the 5' flanking region of the IL12RB2 gene were analysed to determine potential immunogenetic factors affecting CMI responses, using leprosy as a model. METHODS: Polymorphisms in the 5' flanking region of IL12RB2 were examined using direct sequencing techniques, and allele frequencies between patients with lepromatous leprosy and patients with tuberculoid leprosy were compared. The effect of these single nucleotide polymorphisms (SNPs) on IL12RB2 expression was estimated using the dual luciferase reporter gene assay in Jurkat T cells. RESULTS: Several SNPs, including -1035A>G, -1023A>G, -650delG, and -465A>G, were detected within the 5' flanking region of IL12RB2. The frequency of haplotype 1 (-1035A, -1023A, -650G, -464A) was high in the general Japanese population, but was significantly lower in lepromatous patients compared with tuberculoid patients and healthy controls. Reporter gene assays using Jurkat T cells revealed that all haplotypes carrying one or more SNP exhibited a lower transcriptional activity compared with haplotype 1. CONCLUSION: SNPs within the 5' flanking region of IL12RB2 affect the degree of expression of this gene and may be implicated in individual differences in CMI responsiveness to mycobacterial antigens, leading to lepromatous or tuberculoid leprosy.

Identification of a 68 kd surface antigen of Mycobacterium avium that binds to human macrophages.

Infection caused by Mycobacterium avium is the major cause of bacteremia in patients with AIDS. A critical event in the initiation of a variety of bacterial infections is the adherence of bacteria to host cell surfaces, which is often brought about by the interaction of specific molecules on the bacterial surface with host cell surface receptors. In the present study, a sonicate of M. avium was used to isolate monocyte-binding proteins by affinity chromatography with CNBr-Sepharose-4B coupled to extracts of monocytes. A 68 kd protein present on the surface of M. avium was identified as one of nine monocyte-binding proteins. This protein was isolated and further characterized. The N-terminal amino acid sequence (22 residues) of the protein was determined and was found to exhibit strong homology with the 65 kd heat shock proteins of M. tuberculosis, M. leprae, and M. bovis. However, a previously characterized monoclonal antibody directed against a 66 kd antigen of M. avium was found to cross-react with the 68 kd protein from M. avium but not with the 65 kd proteins from M. leprae and M. bovis, suggesting that the 68 kd antigen may differ from the 65 kd proteins of M. leprae and M. bovis with respect to certain epitopes. In an in vitro inhibition assay, the 68 kd protein was found to compete with the attachment of intact fluorescein isothiocyanate-labeled M. avium to monocyte-derived macrophages, inhibiting this attachment in a dose-dependent manner up to 42%. The 65 kd proteins of M. leprae and M. bovis, on the other hand, did not appear to inhibit this attachment substantially (13.9% and 14.6%, respectively). These results suggest that the 68 kd protein of M. avium may be involved in binding to receptors on macrophages and help in the attachment of the organism to its host cell.