The study measured 204 immune parameters and found that 77% were dominated by non-heritable influences, while 58% were almost completely determined by non-heritable influences. The authors conclude that variation in blood cell frequencies, functions, and soluble factors is largely driven by non-heritable factors.

Nearly three quarters of immune traits are influenced by genes, according to researchers at King’s College London. The study found that adaptive immune traits were mostly influenced by genetics, while variation in innate responses more often arose from environmental differences.

From the top 151 heritable traits, the authors identified 241 genome-wide significant SNPs within 11 genetic loci. These loci explain up to 36% of the variation of 19 immune traits, and the paper reports heritabilities ranging from 0% to 96% depending on the trait.

By analyzing twin pairs, researchers determined that most of the variability in the immune system is due to environmental factors, rather than genes. The researchers found that non-heritable influences outweighed heredity in about 75% of all the immune parameters, and almost exclusively determined more than half of the parameters. In the seasonal flu vaccine analysis, no detectable contributions from heritable factors were seen in the resulting antibody responses, suggesting that antibody responses are likely due to environmental factors such as previous vaccinations or infections.

Here we analyse 23,394 immune phenotypes in 497 adult female twins. 76% of these traits show a predominantly heritable influence, whereas 24% are mostly influenced by environment. Using Falconer’s formula to estimate heritability, the mean genetic influence was ~45%, with almost one in eight immune traits above 80%. Although leukocyte subsets are influenced by genetics and environment, adaptive immune traits are more affected by genetics, whereas innate immune traits are more affected by environment.

"Genetic variation accounts for 20–40% of immune variation, with enrichment of gene variants associated with autoimmunity, inflammatory disease, and response to infection." "Twin studies have revealed that a large proportion of the variance in immune traits is explained by non-heritable factors, such as age, sex, and latent infections, notably cytomegalovirus." "Overall, current evidence suggests that while genetics plays an important role in shaping immune variation, non-heritable influences are the major contributors to inter-individual differences in immune parameters."

In a twin study of immune-system traits, the investigators reported that in three-quarters of the measurements, nonheritable influences such as microbial exposure, toxic exposures, vaccinations, diet, and dental hygiene outweighed heritable ones. The article says environment, more than heredity, played the starring role in shaping the human immune system.

Twin and family-based studies provide heritability estimates of 20%–40% on average, but the range across individual cellular or cytokine traits is wide. This review links earlier studies showing both strong genetic effects on some adaptive immune traits and strong environmental effects on many innate traits.

"Here, we use systems immunology to investigate the genetic and environmental drivers of immune variation in Belgian White Blue male cattle." "In contrast to immune cell profiles, genetic factors accounted for the largest proportion of variance in cytokine traits, consistent with human studies." "These results also show that, although genetics is the most important factor contributing to interindividual variation in cytokine production (mean heritability = 0.241, ranging from 1e−06 to 0.756), the majority of the variation in our population could still be explained by nongenetic factors, which is consistent with human studies."

A study of innate immune-cell variation found that natural variation in innate immune cell parameters is preferentially driven by genetic factors. The paper is cited as evidence that at least some immune-system traits are more strongly shaped by genetics than by environment.

"However, this premise has been challenged by recent studies suggesting that people are not all equally equipped to deal with pathogens. Age, sex, infection history, and genetics can affect the immune system and make people more prone to disease." "The two studies confirm that immune variation among individuals is largely due to differences in sex and age." "Natural variation in the parameters of innate immune cells is preferentially driven by genetic factors, Nature Immunology (2018)."

Researchers at King’s are adding to a growing body of evidence that the genetic influence on our immune system is significantly higher than previously thought.[6] The scientists have found that nearly three quarters of immune traits are influenced by genes.[6] They found that adaptive immune traits – the more complex responses that develop after exposure to a specific pathogen, such as chickenpox – are mostly influenced by genetics.[6] They also highlight the importance of environmental influences such as our diet, on shaping the innate immunity (the simple core immune response found in all animals) in adult life.[6] In contrast, variation in innate responses (the simple non specific immune response) more often arose from environmental differences.[6]

A study of twins conducted by Swedish and American investigators shows that our environment, not our heredity, plays the starring role in determining the state of our immune system, the body’s primary defense against disease. “We found that in three-quarters of the measurements, non-heritable influences such as previous microbial or toxic exposures, vaccinations, diet and dental hygiene trumped heritable ones when it came to accounting for differences within a pair of twins”, said lead author Petter Brodin. Variation in the human immune system is largely driven by non-heritable influences.

Based on a recent study of twins led by Stanford University immunologist Mark Davis, the environment may play a larger role than genetics in shaping an individual’s immune system.[5] His team collected and analyzed immune cells and other blood components from 210 pairs of twins, both identical and fraternal, ranging from 8 to 82 years old.[5] Specifically, in about three-fourths of the parameters, the environment seemed to play the biggest role.[5] The differences in the immune systems of identical twins could not be explained by the slight genetic variation between them.[5]

Of the traits considered in the study, "76% … show a predominantly heritable influence, whereas 24% are mostly influenced by environment," wrote the study’s authors.[2] "These data highlight the importance of shared childhood environmental influences such as diet, infections, or microbes in shaping immune homeostasis for monocytes, B1 cells, γδ T cells, and NKT cells, whereas dendritic cells, B2 cells, CD4+ T and CD8+ T cells are more influenced by genetics."[2] "Although leukocyte subsets are influenced by genetics and environment," the authors added, "adaptive immune traits are more affected by genetics, whereas innate immune traits are more affected by environment."[2]

Environmental factors shape the immune system’s reactions more than genes do, a study of twins suggests. The researchers measured 204 immune system characteristics, including numbers of various types of immune cells, levels of immune chemicals and proteins in the blood, and reactions to flu vaccines. Environment played the strongest role in 77 percent of the traits measured and is probably the sole determinant for 58 percent of them, the team found. Genes played a bigger role in the immune reactions of younger twins, the researchers found. But environmental factors gradually swamped that influence as the twins aged and lived apart.

A twin study on 43 MZ and 147 DZ twin pairs estimated heritability at 51% in the antibody responses to the Hib conjugate vaccine. This study thus found substantial heritable variation in vaccine-induced antibody levels. The review notes that heritable variation among hosts in infectious disease traits can be considerable, with heritability estimates for diverse immune-related phenotypes ranging from low to quite high depending on trait and context.

"Large-scale single-cell genomics projects have revolutionized our understanding of human immune variation." "CIMA’s multiomics analyses reveal apparent population-specific genetic effects." "Through this analysis, they were able to identify ~1,200 significant variant→gene or variant→chromatin→trait associations across more than 150 immune-related traits… highlighting that for most immune traits, the causal variant’s impact is channeled through one specific cellular niche."

Twin studies are powerful tools to discriminate whether a complex disease is due to genetic or environmental factors. Concordance rates for autoimmune diseases in monozygotic versus dizygotic twins often suggest a significant genetic component, but incomplete concordance also indicates an important role for environmental influences. Thus, both genetic and environmental factors contribute to the development of autoimmune disease phenotypes.

"In this chapter, I discuss the ways in which host immune responses vary genetically. Host variability affects the relative success of different parasite genotypes and determines the outcome of infection." "Genetic variation among hosts in components of the immune system can be substantial, and this variation can have important consequences for resistance or susceptibility to particular pathogens."

"Here, we discuss the role that natural selection has played in driving phenotypic differences in immune responses across populations." "Patterns of genetic diversity at immune loci indicate strong historical selection by pathogens, which has shaped population-level variation in immune traits." "Nonetheless, environmental heterogeneity and variable pathogen exposure continue to contribute substantially to immune diversity within and between populations."

This study is a comprehensive assessment of the impact of environmental and genetic host factors on circulating cell populations, focusing on both T cells and B cells.[8] We showed that T cell counts were mainly driven by environmental factors, while B cell traits were more influenced by genetic factors.[8] These findings indicate that environmental exposures can shape T cell homeostasis over the life course, whereas B cell phenotypes have a stronger heritable component.[8]

"Increasingly, scientists are discovering how a person’s genes shape the immune system’s ability to fight viruses, identifying certain genetic variations that make people more prone, or less, to viral illnesses." "Immunologist Dusan Bogunovic, PhD, is leading efforts to understand these genetic variations and use that information to help patients." "Studies of inborn errors of immunity show that single-gene mutations can dramatically alter antiviral defenses, underscoring the role of genetics in immune variation."

Since identical twins often have similar environments, this information by itself does not distinguish between the effects of heredity and environment. When identical twins reared apart are more similar than nonidentical twins reared together, genetic factors are implicated. Twin studies in human genetics have been widely used to estimate the relative contributions of genetic and environmental variation to traits, but their interpretation depends on several assumptions about shared environments and genetic relatedness.

"Population-based, systems-level studies of vaccination provide predictors of immune-response quality." "Utilizing population variation, vaccination, and systems biology has revealed that both genetic polymorphisms and environmental exposures (such as prior infections and microbiota composition) shape the magnitude and quality of vaccine-induced immune responses." "These approaches highlight complex interactions between host genetics and environment in determining immune-response variability."

A wide variety of factors—both genetic and environmental—influence the human immune system. Genes set up the basic architecture and potential range of immune responses, but exposures to pathogens, vaccines, diet, microbiome composition and other environmental influences continuously shape immune traits throughout life. For many measured immune system parameters in adults, studies have found that environmental variation explains more of the observed differences between individuals than genetic variation does, although some specific adaptive immune traits show high heritability.

Genetic susceptibility was mentioned with more variability in terms of bivariate variability, so detailed conclusions cannot be drawn from this overview.[10] The Facebook post relays findings from a twin study indicating that environment, more than genetics, shapes the human immune system and that environment overshadowed inheritance in most immune parameters measured.[10]