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Bronikowski AM, Hedrick AR, Kutz GA, Holden KG, Reinke B, Iverson JB. Sex-specific innate immunity and ageing in long-lived fresh water turtles (Kinosternon flavescens: Kinosternidae). Immun Ageing 2023; 20:11. [PMID: 36894996 PMCID: PMC9997018 DOI: 10.1186/s12979-023-00335-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 02/27/2023] [Indexed: 03/11/2023]
Abstract
BACKGROUND The progressive deregulation of the immune system with age, termed immunosenescence, has been well studied in mammalian systems, but studies of immune function in long-lived, wild, non-mammalian populations are scarce. In this study we leverage a 38-year mark-recapture study to quantify the relationships among age, sex, survival, reproductive output and the innate immune system in a long-lived reptile, yellow mud turtles (Kinosternon flavescens; Testudines; Kinosternidae). METHODS We estimated rates of survival and age-specific mortality by sex based on mark-recapture data for 1530 adult females and 860 adult males over 38 years of captures. We analyzed bactericidal competence (BC), and two immune responses to foreign red blood cells - natural antibody-mediated haemagglutination (NAbs), and complement-mediated haemolysis ability (Lys) - in 200 adults (102 females; 98 males) that ranged from 7 to 58 years of age captured in May 2018 during their emergence from brumation, and for which reproductive output and long-term mark-recapture data were available. RESULTS We found that females are smaller and live longer than males in this population, but the rate of accelerating mortality across adulthood is the same for both sexes. In contrast, males exhibited higher innate immunity than females for all three immune variables we measured. All immune responses also varied inversely with age, indicating immunosenescence. For females that reproduced in the preceding reproductive season, egg mass (and therefore total clutch mass) increased with age,. In addition to immunosenescence of bactericidal competence, females that produced smaller clutches also had lower bactericidal competence. CONCLUSIONS Contrary to the general vertebrate pattern of lower immune responses in males than females (possibly reflecting the suppressive effects of androgens), we found higher levels of all three immune variables in males. In addition, contrary to previous work that found no evidence of immunosenescence in painted turtles or red-eared slider turtles, we found a decrease in bactericidal competence, lysis ability, and natural antibodies with age in yellow mud turtles.
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Affiliation(s)
- Anne M Bronikowski
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA. .,Department of Integrative Biology, Kellogg Biological Station, Michigan State University, 3700 E. Gull Lake Rd., Hickory Corners, MI, 49060, USA.
| | - Ashley R Hedrick
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Greta A Kutz
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Kaitlyn G Holden
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Beth Reinke
- Department of Biology, Northeastern Illinois University, Chicago, IL, 60625, USA
| | - John B Iverson
- Department of Biology, Earlham College, Richmond, IN, 47374, USA.
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Past, Present, and Future of Naturally Occurring Antimicrobials Related to Snake Venoms. Animals (Basel) 2023; 13:ani13040744. [PMID: 36830531 PMCID: PMC9952678 DOI: 10.3390/ani13040744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/10/2023] [Accepted: 02/11/2023] [Indexed: 02/22/2023] Open
Abstract
This review focuses on proteins and peptides with antimicrobial activity because these biopolymers can be useful in the fight against infectious diseases and to overcome the critical problem of microbial resistance to antibiotics. In fact, snakes show the highest diversification among reptiles, surviving in various environments; their innate immunity is similar to mammals and the response of their plasma to bacteria and fungi has been explored mainly in ecological studies. Snake venoms are a rich source of components that have a variety of biological functions. Among them are proteins like lectins, metalloproteinases, serine proteinases, L-amino acid oxidases, phospholipases type A2, cysteine-rich secretory proteins, as well as many oligopeptides, such as waprins, cardiotoxins, cathelicidins, and β-defensins. In vitro, these biomolecules were shown to be active against bacteria, fungi, parasites, and viruses that are pathogenic to humans. Not only cathelicidins, but all other proteins and oligopeptides from snake venom have been proteolyzed to provide short antimicrobial peptides, or for use as templates for developing a variety of short unnatural sequences based on their structures. In addition to organizing and discussing an expressive amount of information, this review also describes new β-defensin sequences of Sistrurus miliarius that can lead to novel peptide-based antimicrobial agents, using a multidisciplinary approach that includes sequence phylogeny.
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Palacios MG, Bronikowski AM, Amer A, Gangloff EJ. Transgenerational effects of maternal corticosterone across early life in a viviparous snake. Gen Comp Endocrinol 2023; 331:114162. [PMID: 36356645 DOI: 10.1016/j.ygcen.2022.114162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 10/28/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022]
Abstract
Glucocorticoids (GCs) are central mediators of vertebrate responses to intrinsic and extrinsic stimuli. Among the sources of variation in circulating GCs are transgenerational effects mediated by mothers. Here we studied potential maternal effects mediated by GCs on offspring phenotype in a live-bearing reptile, the western terrestrial garter snake (Thamnophis elegans). We evaluated the association between baseline corticosterone (CORT) levels during gestation (i.e., preparturition) in field-captured mothers and 1) reproductive success and offspring sex ratios, 2) birth phenotypic traits of offspring born under common-garden laboratory conditions, and 3) neonate (age 3 months) and juvenile (age 12 months) traits of offspring raised under two thermal regimes ('warm' and 'cool') during their first year of life. Reproductive success and offspring sex ratios were not associated with preparturition maternal CORT, but pregnant snakes with higher CORT levels gave birth to smaller, lighter offspring, which tended to grow faster to age three months. Neonate baseline CORT varied with preparturition maternal CORT in a sex-specific manner (positive trend for females, negative for males). Maternal CORT effects on offspring phenotype were no longer detectable in juveniles at age one year. Instead, juvenile phenotypes were most influenced by rearing environment, with offspring raised under the cool regime showing higher baseline CORT and slower growth than those raised under warmer conditions. Our findings support the notion that offspring phenotype might be continuously adjusted in response to environmental cues -both pre- and post-natal- and that the strength of maternal CORT effects declines as offspring develop and experience unique environmental challenges. Our results contribute to a growing literature on transgenerational effects of hormones and help to fill a gap in our knowledge of these effects in ectothermic amniotes.
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Affiliation(s)
- Maria G Palacios
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA; Centro Para el Estudio de Sistemas Marinos, CCT CONICET-CENPAT, Blvd. Brown 2915, Puerto Madryn, Chubut, Argentina.
| | - Anne M Bronikowski
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA; Kellogg Biological Station, Michigan State University, Hickory Corners, MI, USA
| | - Ali Amer
- Department of Biological Sciences, Ohio Wesleyan University, Delaware, OH, USA
| | - Eric J Gangloff
- Department of Biological Sciences, Ohio Wesleyan University, Delaware, OH, USA
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Bronikowski AM, Meisel RP, Biga PR, Walters J, Mank JE, Larschan E, Wilkinson GS, Valenzuela N, Conard AM, de Magalhães JP, Duan J, Elias AE, Gamble T, Graze R, Gribble KE, Kreiling JA, Riddle NC. Sex-specific aging in animals: Perspective and future directions. Aging Cell 2022; 21:e13542. [PMID: 35072344 PMCID: PMC8844111 DOI: 10.1111/acel.13542] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 11/15/2021] [Accepted: 12/11/2021] [Indexed: 12/14/2022] Open
Abstract
Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age-associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer-lived females, species where males live longer, and species lacking sex differences in lifespan. The underlying causes of sex differences in aging remain mostly unknown. Currently, we do not understand the molecular drivers of sex differences in aging, or whether they are related to the accepted hallmarks or pillars of aging or linked to other well-characterized processes. In particular, understanding the role of sex-determination mechanisms and sex differences in aging is relatively understudied. Here, we take a comparative, interdisciplinary approach to explore various hypotheses about how sex differences in aging arise. We discuss genomic, morphological, and environmental differences between the sexes and how these relate to sex differences in aging. Finally, we present some suggestions for future research in this area and provide recommendations for promising experimental designs.
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Affiliation(s)
- Anne M. Bronikowski
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowaUSA
| | - Richard P. Meisel
- Department of Biology and BiochemistryUniversity of HoustonHoustonTexasUSA
| | - Peggy R. Biga
- Department of BiologyThe University of Alabama at BirminghamBirminghamAlabamaUSA
| | - James R. Walters
- Department of Ecology and Evolutionary BiologyThe University of KansasLawrenceKansasUSA
| | - Judith E. Mank
- Department of ZoologyUniversity of British ColumbiaVancouverBritish ColumbiaCanada
- Department of BioscienceUniversity of ExeterPenrynUK
| | - Erica Larschan
- Department of Molecular Biology, Cell Biology and BiochemistryBrown UniversityProvidenceRhode IslandUSA
| | | | - Nicole Valenzuela
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowaUSA
| | - Ashley Mae Conard
- Department of Computer ScienceCenter for Computational and Molecular BiologyBrown UniversityProvidenceRhode IslandUSA
| | - João Pedro de Magalhães
- Integrative Genomics of Ageing GroupInstitute of Ageing and Chronic DiseaseUniversity of LiverpoolLiverpoolUK
| | | | - Amy E. Elias
- Department of Molecular Biology, Cell Biology and BiochemistryBrown UniversityProvidenceRhode IslandUSA
| | - Tony Gamble
- Department of Biological SciencesMarquette UniversityMilwaukeeWisconsinUSA
- Milwaukee Public MuseumMilwaukeeWisconsinUSA
- Bell Museum of Natural HistoryUniversity of MinnesotaSaint PaulMinnesotaUSA
| | - Rita M. Graze
- Department of Biological SciencesAuburn UniversityAuburnAlabamaUSA
| | - Kristin E. Gribble
- Josephine Bay Paul Center for Comparative Molecular Biology and EvolutionMarine Biological LaboratoryWoods HoleMassachusettsUSA
| | - Jill A. Kreiling
- Department of Molecular Biology, Cell Biology and BiochemistryBrown UniversityProvidenceRhode IslandUSA
| | - Nicole C. Riddle
- Department of BiologyThe University of Alabama at BirminghamBirminghamAlabamaUSA
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Holden KG, Gangloff EJ, Miller DAW, Hedrick AR, Dinsmore C, Basel A, Kutz G, Bronikowski AM. Over a decade of field physiology reveals life-history specific strategies to drought in garter snakes ( Thamnophis legans). Proc Biol Sci 2022; 289:20212187. [PMID: 35078358 PMCID: PMC8790353 DOI: 10.1098/rspb.2021.2187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Changing climates and severe weather events can affect population viability. Individuals need to buffer such negative fitness consequences through physiological plasticity. Whether certain life-history strategies are more conducive to surviving changing climates is unknown, but theory predicts that strategies prioritizing maintenance and survival over current reproduction should be better able to withstand such change. We tested this hypothesis in a meta-population of garter snakes having naturally occurring variation in life-history strategies. We tested whether slow pace-of-life (POL) animals, that prioritize survival over reproduction, are more resilient than fast POL animals as measured by several physiological biomarkers. From 2006 to 2019, which included two multi-year droughts, baseline and stress-induced reactivity of plasma corticosterone and glucose varied annually with directionalities consistent with life-history theory. Slow POL animals exhibited higher baseline corticosterone and lower baseline glucose, relative to fast POL animals. These patterns were also observed in stress-induced measures; thus, reactivity was equivalent between ecotypes. However, in drought years, measures of corticosterone did not differ between different life histories. Immune cell distribution showed annual variation independent of drought or life history. These persistent physiological patterns form a backdrop to several extirpations of fast POL populations, suggesting a limited physiological toolkit to surviving periods of extreme drought.
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Affiliation(s)
- Kaitlyn G. Holden
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - Eric J. Gangloff
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - David A. W. Miller
- Department of Ecosystem Science and Management, Penn State University, University Park, PA 16802, USA
| | - Ashley R. Hedrick
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - Carli Dinsmore
- Department of Ecosystem Science and Management, Penn State University, University Park, PA 16802, USA
| | - Alison Basel
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - Greta Kutz
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
| | - Anne M. Bronikowski
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, 2200 Osborn Drive, 251 Bessey Hall, Ames, IA 50011, USA
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Robledo-Avila LA, Phillips-Farfán BV, Harfush Meléndez M, Lopez Toledo L, Tafolla Venegas D, Herrera Vargas MA, Ruíz Cortés DV, Meléndez-Herrera E. Short communication: Ex-situ conservation in hatcheries is associated with spleen development in Lepidochelys olivacea turtle hatchlings. Comp Biochem Physiol A Mol Integr Physiol 2021; 265:111130. [PMID: 34954346 DOI: 10.1016/j.cbpa.2021.111130] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 12/20/2021] [Accepted: 12/20/2021] [Indexed: 11/25/2022]
Abstract
Ex-situ conservation in hatcheries is a successful strategy for the recovery of sea turtle populations. However, it alters the ontogenesis of the brain and gonads, as well as body size and locomotor performance at nest emergence. Relocation to hatcheries may alter immune system development, since this depends highly on the nest environment. We hypothesized that ex-situ brooding would negatively associate with immune traits of Lepidochelys olivacea. Splenic cytoarchitecture and leukocyte quantification were used as proxies for the immune configuration. Body size, gonadal sex and sand temperature during incubation were determined. Additionally, the success of nest hatching and emergence was quantified. Linear mixed models of splenic cytoarchitecture, leucocyte proportions and body size, using sex and nest type as explanatory variables, evaluated the effects of ex-situ brooding. Generalized linear mixed models using quasibinomial distributions (log link) analyzed effects on hatching and emergence success. Hatchlings from ex-situ nests were heavier, larger and showed a greater spleen-somatic index. They showed more and better defined splenic periarteriolar lymphoid sheaths, as well as a higher proportion of heterophils but less monocytes. Moreover, ex-situ brooding increased hatching and emergence success. Sand temperatures in hatcheries favored male sex determination, while the opposite occurred for in-situ incubation. Interestingly, the immune configuration and body size were independent of sex but associated with ex-situ conservation. Greater body size promotes early hatchling survival, while better spleen development is related to a greater antibody production and a better immune response to pathogens. Altogether, the results suggest that ex-situ incubation is associated with a better immune configuration and higher survival success.
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Affiliation(s)
- Liliana Areli Robledo-Avila
- Instituto de Investigaciones sobre Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Colonia Nueva Esperanza, C.P. 58337 Morelia, Michoacán, México
| | - Bryan Víctor Phillips-Farfán
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Insurgentes Sur 3700, Letra C, Alcaldía Coyoacán C.P. 04530, Cd. de México, México
| | | | - Leonel Lopez Toledo
- Instituto de Investigaciones sobre Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Colonia Nueva Esperanza, C.P. 58337 Morelia, Michoacán, México
| | - David Tafolla Venegas
- Facultad de Biología, Universidad Michoacana de San Nicolás de Hidalgo, Avenida Francisco J. Múgica s/n, Ciudad Universitaria, 58030 Morelia, Michoacán, México
| | - Ma Antonia Herrera Vargas
- Instituto de Investigaciones sobre Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Colonia Nueva Esperanza, C.P. 58337 Morelia, Michoacán, México
| | - Diana Vanessa Ruíz Cortés
- Instituto de Investigaciones sobre Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Colonia Nueva Esperanza, C.P. 58337 Morelia, Michoacán, México
| | - Esperanza Meléndez-Herrera
- Instituto de Investigaciones sobre Recursos Naturales, Universidad Michoacana de San Nicolás de Hidalgo, Av. San Juanito Itzícuaro s/n, Colonia Nueva Esperanza, C.P. 58337 Morelia, Michoacán, México.
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Gangloff EJ, Leos-Barajas V, Demuth G, Zhang H, Kelly CD, Bronikowski AM. Movement modeling and patterns of within- and among-individual behavioral variation across time scales in neonate garter snakes (Thamnophis elegans). Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03099-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Leivesley JA, Rollinson N. Maternal provisioning and fluctuating thermal regimes enhance immune response in a reptile with temperature-dependent sex determination. J Exp Biol 2021; 224:jeb.237016. [PMID: 33536300 DOI: 10.1242/jeb.237016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 01/22/2021] [Indexed: 11/20/2022]
Abstract
The Charnov-Bull model of differential fitness is often used to explain the evolution and maintenance of temperature-dependent sex determination (TSD). Most tests of the model focus on morphological proxies of fitness, such as size traits, whereas early life physiological traits that are closely related to lifetime fitness might provide a framework for generalizing the Charnov-Bull model across taxa. One such trait is the strength of the early-life immune response, which is strongly linked to early-life survival and fitness. Here, we manipulated temperature, variance in temperature, and sex to test the Charnov-Bull model using a physiological trait, immune system strength, in the snapping turtle (Chelydra serpentina). We found no evidence of sex-specific differences in bactericidal capacity of hatchling blood, and no evidence that mean temperature influences bactericidal capacity. However, we did find that fluctuating incubation temperature (i.e. a more naturalized incubation regime) is associated with a greater bactericidal capacity compared with constant temperature incubation. We also found that egg mass, a proxy for maternal provisioning, is positively associated with bactericidal capacity. Our findings suggest that the evolution of temperature-dependent sex determination in reptiles is unrelated to our measure of early-life innate immunity. Our study also underlines how immune response is condition dependent in early life, and questions the biological relevance of constant temperature incubation in experimental studies on ectotherm development.
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Affiliation(s)
- Jessica Alice Leivesley
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2
| | - Njal Rollinson
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada, M5S 3B2.,School of the Environment, University of Toronto, Toronto, ON, Canada, M5S 3E8
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Zimmerman LM. The reptilian perspective on vertebrate immunity: 10 years of progress. J Exp Biol 2020; 223:223/21/jeb214171. [DOI: 10.1242/jeb.214171] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
ABSTRACT
Ten years ago, ‘Understanding the vertebrate immune system: insights from the reptilian perspective’ was published. At the time, our understanding of the reptilian immune system lagged behind that of birds, mammals, fish and amphibians. Since then, great progress has been made in elucidating the mechanisms of reptilian immunity. Here, I review recent discoveries associated with the recognition of pathogens, effector mechanisms and memory responses in reptiles. Moreover, I put forward key questions to drive the next 10 years of research, including how reptiles are able to balance robust innate mechanisms with avoiding self-damage, how B cells and antibodies are used in immune defense and whether innate mechanisms can display the hallmarks of memory. Finally, I briefly discuss the links between our mechanistic understanding of the reptilian immune system and the field of eco-immunology. Overall, the field of reptile immunology is poised to contribute greatly to our understanding of vertebrate immunity in the next 10 years.
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The conundrum of human immune system "senescence". Mech Ageing Dev 2020; 192:111357. [PMID: 32949594 PMCID: PMC7494491 DOI: 10.1016/j.mad.2020.111357] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 09/01/2020] [Accepted: 09/08/2020] [Indexed: 12/15/2022]
Abstract
Biomarkers of human immunosenescence are discussed. Longitudinal studies are essential. Associations of immune markers in older adults with clinical outcome are context-dependent. There are no universal biomarkers of human immunosenescence. There are common age-associated changes to peripheral immune markers in humans.
There is a great deal of debate on the question of whether or not we know what ageing is (Ref. Cohen et al., 2020). Here, we consider what we believe to be the especially confused and confusing case of the ageing of the human immune system, commonly referred to as “immunosenescence”. But what exactly is meant by this term? It has been used loosely in the literature, resulting in a certain degree of confusion as to its definition and implications. Here, we argue that only those differences in immune parameters between younger and older adults that are associated in some definitive manner with detrimental health outcomes and/or impaired survival prospects should be classed as indicators of immunosenescence in the strictest sense of the word, and that in humans we know remarkably little about their identity. Such biomarkers of immunosenescence may nonetheless indicate beneficial effects in other contexts, consistent with the notion of antagonistic pleiotropy. Identifying what could be true immunosenescence in this respect requires examining: (1) what appears to correlate with age, though generality across human populations is not yet confirmed; (2) what clearly is part of a suite of canonical changes in the immune system that happen with age; (3) which subset of those changes accelerates rather than slows aging; and (4) all changes, potentially population-specific, that accelerate agig. This remains an immense challenge. These questions acquire an added urgency in the current SARS-CoV-2 pandemic, given the clearly greater susceptibility of older adults to COVID-19.
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