Human CD4 and CD8 regulatory T cells in infectious diseases and vaccination

Neutralization of interleukin-10 from CD14(+) monocytes enhances gamma interferon production in peripheral blood mononuclear cells from Mycobacterium avium subsp. paratuberculosis-infected goats

The gamma interferon assay is used to identify Mycobacterium avium subsp. paratuberculosis-infected animals. It has been suggested that regulatory mechanisms could influence the sensitivity of the test when it is performed with cells from cattle and that the neutralization of interleukin-10 (IL-10) in vitro would increase the gamma interferon responses. To investigate the regulatory mechanisms affecting the gamma interferon assay with cells from goats, blood was collected from M. avium subsp. paratuberculosis-infected, M. avium subsp. paratuberculosis-exposed, and noninfected goats. Neutralization of IL-10 by a monoclonal antibody resulted in increased levels of gamma interferon production in M. avium subsp. paratuberculosis purified protein derivative (PPDj)-stimulated samples from both infected and exposed goats. However, the levels of gamma interferon release were also increased in unstimulated cells and in PPDj-stimulated cells from some noninfected animals following neutralization. Depletion of putative regulatory CD25(high) T cells had no clear effect on the number of gamma-interferon-producing cells. The IL-10-producing cells were identified to be mainly CD14(+) major histocompatibility complex class II-positive monocytes in both PPDj-stimulated and control cultures and not regulatory T cells. However, possible regulatory CD4(+) CD25(+) T cells produced IL-10 in response to concanavalin A stimulation. The numbers of CD4(+), CD8(+), and CD8(+) gammadelta T-cell receptor-positive cells producing gamma interferon increased following IL-10 neutralization. These results provide insight into the source and the role of IL-10 in gamma interferon assays with cells from goats and suggest that IL-10 from monocytes can regulate both innate and adaptive gamma interferon production from several cell types. Although IL-10 neutralization increased the sensitivity of the gamma interferon assay, the specificity of the test could be compromised.

Interplay between virus-specific effector response and Foxp3 regulatory T cells in measles virus immunopathogenesis

Measles is a highly contagious childhood disease associated with an immunological paradox: although a strong virus-specific immune response results in virus clearance and the establishment of a life-long immunity, measles infection is followed by an acute and profound immunosuppression leading to an increased susceptibility to secondary infections and high infant mortality. In certain cases, measles is followed by fatal neurological complications. To elucidate measles immunopathology, we have analyzed the immune response to measles virus in mice transgenic for the measles virus receptor, human CD150. These animals are highly susceptible to intranasal infection with wild-type measles strains. Similarly to what has been observed in children with measles, infection of suckling transgenic mice leads to a robust activation of both T and B lymphocytes, generation of virus-specific cytotoxic T cells and antibody responses. Interestingly, Foxp3(+)CD25(+)CD4(+) regulatory T cells are highly enriched following infection, both in the periphery and in the brain, where the virus intensively replicates. Although specific anti-viral responses develop in spite of increased frequency of regulatory T cells, the capability of T lymphocytes to respond to virus-unrelated antigens was strongly suppressed. Infected adult CD150 transgenic mice crossed in an interferon receptor type I-deficient background develop generalized immunosuppression with an increased frequency of CD4(+)CD25(+)Foxp3(+) T cells and strong reduction of the hypersensitivity response. These results show that measles virus affects regulatory T-cell homeostasis and suggest that an interplay between virus-specific effector responses and regulatory T cells plays an important role in measles immunopathogenesis. A better understanding of the balance between measles-induced effector and regulatory T cells, both in the periphery and in the brain, may be of critical importance in the design of novel approaches for the prevention and treatment of measles pathology.

Variation in the IL7RA and IL2RA genes in German multiple sclerosis patients

Variation in the genes encoding the interleukin (IL) 7 and IL2 receptor alpha chains (IL7RA, IL2RA) was recently found associated with multiple sclerosis (MS). We evaluated the role of these two genes in a large German MS case-control cohort. Five single nucleotide polymorphisms (SNPs) in IL7RA and four in IL2RA were genotyped in 1319 MS patients and 908 controls by means of restriction enzyme digestion or TaqMan assays and subsequently evaluated for association with MS. IL7RA expression was measured via quantitative real time PCR in 24 subjects. We replicated the association of exon 6 variation (rs6897932) in IL7RA with MS. Yet, this association was only found in patients with primary progressive (pp) or secondary progressive (sp) disease course (p=0.0004). Expression analysis did not show differences in IL7RA expression depending on genotypes at this locus, while reduced expression of the soluble receptor was observed in patients with pp and sp MS irrespective of genotype. In the IL2RA gene, significant associations of SNPs in introns 3 and 7 with MS subtypes were obvious. Together these results confirm involvement of polymorphisms in the IL7RA and IL2RA genes in MS pathogenesis and suggest that IL7RA variation may primarily affect chronic disease courses.