Combined TCRG and TCRA TREC analysis reveals increased peripheral T-lymphocyte but constant intra-thymic proliferative history upon ageing

T-cell receptor (TCR) repertoire diversity, thymic output, clonal size and peripheral T-lymphocyte numbers largely depend on intra-thymic and post-thymic T-lymphocyte proliferation. However, quantitative insight into thymocyte and T-lymphocyte proliferation is still lacking. We developed a new TCRG-based TCR excision circle (TREC) assay, the Vγ-Jγ TREC assay, which we used together with an adjusted δREC-ψJα TREC assay to quantify the proliferative history of human thymocyte and T-lymphocyte subpopulations from children and adults. This revealed that thymocytes undergo ～6–8 intra-thymic cell divisions from the double negative (DN) 3 developmental stage onwards, which appeared independent of age. Thus thymocyte proliferation after the DN3 developmental stages is stable and therefore not contributing to the reduced thymic output upon ageing. Cord blood naive T lymphocytes had already undergone ～2–3 post-thymic cell divisions, which increased to ～6–7 cell divisions in naive T lymphocytes of middle-aged adults, indicating the importance of homeostatic naive T-lymphocyte proliferation from a young age onwards in the maintenance of peripheral T-lymphocyte numbers. In conclusion, our data provide quantitative insight into the proliferative history of thymocyte and T-lymphocyte subpopulations and alterations herein upon ageing. This novel TREC assay approach could prove valuable in immune status monitoring in a variety of conditions.     

Dynamic changes of the neurogenic potential in the rat cochlear nucleus during post-natal development

Neuronal stem cells have been described in the post-natal cochlear nucleus recently. The aim of the study was to analyse the neurogenic potential in the cochlear nucleus from the early post-natal days until adulthood. Cochlear nuclei from Sprague–Dawley rats from post-natal day P3 up to P40 were examined. Neurosphere assays showed persistent neurosphere formation from the early post-natal days until adulthood. The numbers of generated neurospheres were fewer in older ages. Neurospheres were smaller, but displayed the same pattern of neuronal stem cell markers. The markers GFAP, MBP and ß-III Tubulin showed differentiation of dissociated cells from the neurospheres in all cells of the neuronal lineage. BrdU incorporation could be detected, in an age-dependent decrease, in whole-mount experiments of the cochlear nucleus on all examined days. BrdU co-labelled with Atoh1 and ß-III Tubulin. In addition, gene expression and cellular distribution studies of the neuronal stem cell markers displayed an age-dependent reduction in both quantity and numbers. The presented results display a possible neurogenic potential until adulthood in the cochlear nucleus by in vitro and in vivo experiments. The fact that this potential is highest at a critical period of development reveals possible functional importance for the development of the cochlear nucleus and the auditory function. The persistent neurogenic potential displayed until adulthood could be a neurogenic niche in the adult cochlear nucleus, which might be used for potential therapeutic strategies.     

Attempted Passive Prophylaxis with a Monoclonal Anti-Burkholderia Pseudomallei Exopolysaccharide Antibody in a Murine Model of Melioidosis

Melioidosis is a severe gram-negative infection caused by the facultative intracellular bacterium Burkholderia pseudomallei, which is responsible for a broad spectrum of symptoms in both humans and animals. No licensed vaccine currently exists. This study evaluated the protective effect of a monoclonal antibody (Mab Ps6F6) specific to B. pseudomallei exopolysaccharide in an outbred murine model of sub-acute melioidosis. When administered before the infectious challenge, Ps6F6 significantly increased resistance to infection and restrained bacterial burden in the spleen over a 30-days period. Patterns of IFN-γ production were similar in the treated and non treated groups of mice. However, Ps6F6 lowered IFN-γ levels over the duration of the assay period, except on day 1, suggesting a transient and rapid production of IFN-γ under Ps6F6 control. Minor but persisting increases occurred in IL-12 levels while TNF-α was detected only in the controls at the later stages of infection. No IL-10 secretion was detected in both groups of mice. These data suggest that passive prophylaxis with Mab Ps6F6 provide a moderate and transient induction of inflammatory responses in infected mice but failed to trigger a sterilizing protective immunity.     

Patients treated with high‐dose intravenous immunoglobulin show selective activation of regulatory T cells

Intravenous immunoglobulin (IVIg) is used to treat autoimmune and systemic inflammatory diseases caused by derailment of humoral and cellular immunity. In this study we investigated whether IVIg treatment can modulate regulatory T cells (T_regs) in humans in vivo. Blood was collected from IVIg-treated patients with immunodeficiency or autoimmune disease who were treated with low-dose (n = 12) or high-dose (n = 15) IVIg before, immediately after and at 7 days after treatment. Percentages and activation status of circulating CD4⁺CD25⁺forkhead box protein 3 (FoxP3⁺) T_regs and of conventional CD4⁺FoxP3⁻ T-helper cells (T_conv) were measured. The suppressive capacity of T_regs purified from blood collected at the time-points indicated was determined in an ex-vivo assay. High-dose, but not low-dose, IVIg treatment enhanced the activation status of circulating T_regs, as shown by increased FoxP3 and human leucocyte antigen D-related (HLA-DR) expression, while numbers of circulating T_regs remained unchanged. The enhanced activation was sustained for at least 7 days after infusion, and the suppressive capacity of purified T_regs was increased from 41 to 70% at day 7 after IVIg treatment. The activation status of T_conv was not affected by IVIg. We conclude that high-dose IVIg treatment activates T_regs selectively and enhances their suppressive function in humans in vivo. This effect may be one of the mechanisms by which IVIg restores imbalanced immune homeostasis in patients with autoimmune and systemic inflammatory disorders.     

Determinants and Reference Ranges of Serum Immunoglobulins in Middle-Aged and Elderly Individuals: a Population-Based Study

Purpose

In clinical practice, currently one reference range for serum immunoglobulin (Ig) A, G, and M is applied to all adults, although various factors may influence Ig serum levels. Population-based data on determinants of IgA, IgG, and IgM and recommendations for subgroup specific reference ranges are lacking. We aimed to provide an overview of determinants of IgA, IgG, and IgM in community-dwelling middle-aged and elderly individuals and explore determinants that influence Ig reference ranges.

Methods

Within the Rotterdam Study, we performed linear regression analyses for the association of demographic, lifestyle, and cardiovascular factors with serum IgA, IgG, and IgM. We furthermore calculated Ig reference ranges (based on percentiles), both overall and within relevant subgroups.

Results

We included 8768 participants (median age 62 years). IgA and IgG increased non-linearly with higher age (P?<?.0001 for both). Women had lower IgA (beta:???0.24; 95% confidence interval [95% CI]:???0.29;???0.20) and IgG (beta:???0.33; 95% CI:???0.44;???0.23), but higher IgM levels (beta: 0.08; 95% CI: 0.04;0.13) than men. Former and particularly current smoking were associated with lower IgA and IgG (betas between???0.07 and???1.03). Higher alcohol consumption was associated with lower IgG (beta for heavy drinking:???0.70; 95% CI:???0.91;???0.48). Corticosteroid use was associated with lower IgG (beta:???1.12; 95% CI:???1.58;???0.66). Associations with cardiovascular factors were heterogeneous and differed between sexes.

Conclusion

Age, sex, smoking, alcohol consumption, corticosteroid use, and cardiovascular factors are determinants that should be considered when interpreting serum Ig levels in middle-aged and elderly individuals and may require adjusted reference ranges.

     

Immunohistochemical localization of somatostatin receptor sst2A in human rheumatoid synovium

OBJECTIVE: To identify the somatostatin receptor-expressing cells in rheumatoid synovium using a recently developed antiserum directed against the somatostatin receptor subtype 2A (sst2A). METHODS: We carried out immunohistochemical studies of synovial biopsies from 7 patients with rheumatoid arthritis (RA) and one non-RA patient, using a rabbit polyclonal antiserum directed against sst2A and monoclonal antibodies directed against phenotypic markers. RESULTS: SSt2A was expressed by the endothelial cells of the synovial venules but also by a subset of synovial macrophages. CONCLUSION: The identification of somatostatin receptors on macrophages, which are thought to be important effector cells in RA, may offer mechanistic insights into the potential therapeutic effect of somatostatin (analogs) in RA.