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Background: Selenium is an essential trace element with both beneficial and detrimental effects on health depending on dose and chemical form. Currently, there is debate on recommendations for selenium supplementation as a public health measure to improve immune function and reduce infectious disease susceptibility. Objectives: We performed a systematic review and meta-analysis of experimental studies assessing the effect of selenium supplementation on immunity-related outcomes in healthy people. Methods: We undertook a search of published and unpublished studies in literature databases such as PubMed/MEDLINE, Embase, and clinicaltrials.gov up to 17 October, 2022, and performed a meta-analysis comparing the effects on immunity-related outcomes between Se-supplemented versus control arms. Whenever possible we assessed the nonlinear relation using a dose-response approach. Results: 9 trials were included, 5 in North America, and 4 in Europe, with a duration between 8 and 48 weeks and supplementation of both inorganic and organic selenium forms. Selenium supplementation did not substantially affect immunoglobulin or white blood cell concentrations, and the dose-response meta-analysis indicated that an increase in plasma selenium concentrations above 100 µg/L did not further increase IgA levels nor T cells. An inverted U-shaped relation emerged for NK cell count, with a lower number of these cells both below and above 120 µg/L. The only beneficial effect of selenium supplementation was the increased activity for NK lysis, but the available data did not permit dose-response analysis. Cytokine levels were substantially unaffected by selenium supplementation. Conclusions: Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent and heterogeneous due to differences in trial duration and interventions, plus evidence of null and even detrimental effects. Overall, the evidence that we extracted from the literature in this systematic review does not support the need to supplement selenium beyond the recommended dietary intake to obtain beneficial effects on immune function. This trial was registered at PROSPERO (CRD42022312280). [ABSTRACT FROM AUTHOR]

Aquaculture in North America is currently dominated by Atlantic salmon, but there has been an increasing interest in the production of species native to the Pacific coast. Chinook salmon is relatively new to production; therefore, the selection of appropriate stocks is critical. Often genes from wild populations are incorporated into farmed stocks to avoid performance decreases associated with inbreeding. The present study focuses on assessing the immunological performance of one inbred stock and seven outbred/hybrid crosses after challenge with the marine pathogen, Vibrio anguillarum. Throughout exposure challenge to both pathogen and sterile PBS, significant differences in mortality were observed between crosses. Fish were also assessed for major histocompatibility complex (MHC) class II β1 genotype, and although particular alleles did not confer resistance, crosses with better survival had more individuals presenting a heterozygous genotype. The stress induced during infection resulted in several individuals presenting signs of Bacterial Kidney Disease (Renibacterium salmoninarum) indicating that chronic co‐infection may have contributed to susceptibility. When spleen samples from the highest and lowest performing hybrid crosses were assessed for cytokine and respiratory burst gene expression throughout bacterial challenge, high surviving crosses presented lower expression of inflammatory cytokine transcripts (IL‐1β, IL‐6 and TNFα) when compared to low performing crosses. Interestingly, microsatellite analysis revealed no significant differences in inbreeding coefficient or allelic richness between crosses despite observed variation in immune performance. Understanding the impact of outbreeding on the immune function of farmed, and often inbred, Chinook salmon could aid in future development of high‐quality aquaculture stocks for this species. [ABSTRACT FROM AUTHOR]

A Thoroughbred gelding in North America was evaluated for Actinobacillus peritonitis on three different occasions over a 4-year period. At each presentation, peritoneal fluid had an elevated nucleated cell count (220,000-550,000 cells/µL) characterised by non-degenerate neutrophils, no visible bacteria, an elevated total protein (4.6-5.5 g/dL) and bacterial culture yielding Actinobacillus spp. Actinobacillus peritonitis appears to be a regional disease occurring in Australia and less commonly in New Zealand and North America. Recurrence, other than incomplete resolution, has not been previously reported. This case highlights the classical presentation, response to therapy and excellent prognosis despite the alarmingly abnormal peritoneal fluid characteristic of Actinobacillus peritonitis and questions the role of parasite migration in the pathogenesis. Finally, this case is remarkable because Actinobacillus peritonitis was recurrent over several years in an otherwise normal horse. [ABSTRACT FROM AUTHOR]

Abstract: The trace element selenium (Se) is essential for immune system development and function in animals. However, the exact functions of Se in the human immune system and the achievable health benefits from Se supplementation remain unclear. To test whether an increased intake of dietary Se affects immune function, we conducted a randomized, controlled trial of Se supplementation in healthy free-living men. Forty-two men were administered 300μg of Se a day as high-Se Baker''s yeast, or low-Se yeast for 48 weeks. Serum immunoglobulins, differential complete blood counts and lymphocyte sub-populations were measured every 6 weeks. Tests of delayed-type hypersensitivity (DTH) skin responses to mumps, candida, trychophyton, tuberculin-purified protein, and tetanus were performed at baseline and at the end of 48 weeks of treatment. Supplementation increased blood Se concentration by 50%. Surprisingly, consumption of the low-Se yeast induced anergy in DTH skin responses and increased counts of natural killer (NK) cells and T lymphocytes expressing both subunits of the high affinity interleukin-2 receptor (IL2R). DTH skin responses and IL2R+ cells did not change in the high-Se group, suggesting Se supplementation blocked induction of DTH anergy. There were no differences between groups in quality of life indicators, number of days sick, other leukocyte phenotypes, serum immunoglobulins, or complement factors. These results suggest that Se plays a role in immunotolerization, a cell-mediated process involved in many aspects of immune function. [Copyright &y& Elsevier]