Circulating plasma microRNAs as biomarkers for iron status in blood donors

Iron-Deficiency in Atopic Diseases: Innate Immune Priming by Allergens and Siderophores

Although iron is one of the most abundant elements on earth, about a third of the world's population are affected by iron deficiency. Main drivers of iron deficiency are beside the chronic lack of dietary iron, a hampered uptake machinery as a result of immune activation. Macrophages are the principal cells distributing iron in the human body with their iron restriction skewing these cells to a more pro-inflammatory state. Consequently, iron deficiency has a pronounced impact on immune cells, favoring Th2-cell survival, immunoglobulin class switching and primes mast cells for degranulation. Iron deficiency during pregnancy increases the risk of atopic diseases in children, while both children and adults with allergy are more likely to have anemia. In contrast, an improved iron status seems to protect against allergy development. Here, the most important interconnections between iron metabolism and allergies, the effect of iron deprivation on distinct immune cell types, as well as the pathophysiology in atopic diseases are summarized. Although the main focus will be humans, we also compare them with innate defense and iron sequestration strategies of microbes, given, particularly, attention to catechol-siderophores. Similarly, the defense and nutritional strategies in plants with their inducible systemic acquired resistance by salicylic acid, which further leads to synthesis of flavonoids as well as pathogenesis-related proteins, will be elaborated as both are very important for understanding the etiology of allergic diseases. Many allergens, such as lipocalins and the pathogenesis-related proteins, are able to bind iron and either deprive or supply iron to immune cells. Thus, a locally induced iron deficiency will result in immune activation and allergic sensitization. However, the same proteins such as the whey protein beta-lactoglobulin can also transport this precious micronutrient to the host immune cells (holoBLG) and hinder their activation, promoting tolerance and protecting against allergy. Since 2019, several clinical trials have also been conducted in allergic subjects using holoBLG as a food for special medical purposes, leading to a reduction in the allergic symptom burden. Supplementation with nutrient-carrying lipocalin proteins can circumvent the mucosal block and nourish selectively immune cells, therefore representing a new dietary and causative approach to compensate for functional iron deficiency in allergy sufferers.

Monitoring iron stores in Icelandic blood donors from 1997 through 2019

OBJECTIVES

To estimate the frequency of iron deficiency (ID) and anaemia in blood donors in Iceland and the impact of serum ferritin (SF) testing policy change.

BACKGROUND

Blood donations contribute to ID and/or anaemia in whole blood donors (WBD). SF may be used to monitor blood donor iron stores.

MATERIALS AND METHODS

The study included WBD and new donors (ND) in the Icelandic Blood Bank in 1997-2019. SF was measured for ND and intermittently for WBD until October 2017, but thereafter for all WBD and ND at every visit. In January 2018, the SF threshold increased from 14 to 16 μg/L for ND and from 8 to 10 μg/L for WBD.

RESULTS

The study included 85 370 SF results from 243 369 visits of 32 910 donors. Median SF was higher for males than females, both for ND (88.0 vs. 31.2 μg/L, p < 0.001) and WBD (before 2018: 43.0 vs. 22.0 μg/L, p < 0.001). After the policy change in 2018, median SF increased for both male WBD (to 45.2 μg/L, p < 0.001) and female WBD (to 25.7 μg/L, p < 0.001). ID (SF <15 μg/L) was present in 10.6% of female ND and 0.5% of male ND. After policy change, the proportion of WB donations associated with ID decreased for males (from 6.4% to 4.0%) and females (from 18.9% to 14.1%). ID anaemia was present at some time in 3.7% of female WBD and 1.2% of male WBD.

CONCLUSION

This nationwide study showed that ID in WB donors is common, especially among females, but monitoring SF may improve donor management.