Study reveals that individuals have immune 'personalities'

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Researchers from the University's Institute of Integrative Biology, working with external collaborators have identified consistent individual differences in immunity, or what they call ‘immune personalities’, in a wild population of rodents.

It is well established that different inbred strains of mice, living in simple laboratory environments far removed from nature, differ in the way they respond to infection.

However, little is known about whether these patterns extend to natural populations, and indeed to differences between individuals in natural populations, which are typically made up of genetically-diverse individuals that and face a multiplicity of challenges, parasitological and otherwise.

Consistent differences

A topical example of a varied response to infection in the animal world is TB in badgers. Some animals can carry and transmit TB without showing any symptoms, whereas others become seriously ill.

Researchers, collaborating with the Universities of Nottingham and Salford, aimed to establish whether consistent differences in immune response were visible between individual rodents, specifically field voles, in the wild.

Wild field voles are often found to be infected with a range of different parasites - macroparasites like fleas, ticks and mites, and small microparasites, like viruses and bacteria.

Gene expression

To assess the immune responses of the voles, researchers, led by Professor Mike Begon, individually marked field voles and then monitored them over time, as a series of captures and recaptures. They collected a blood sample on each capture to enable them to examine the expression levels of specific immune genes.

Gene expression is the process by which a gene is activated to produce a required protein, in this case an immune protein.

As the researchers had access to a wealth of knowledge about these voles (e.g. body condition, sex, site of capture and parasites), they were able to account for these other sources of immune variation in order to look for underlying consistencies in immunity.

Immune genes

The study, which has been published by PLOS ONE, found some evidence for consistent differences between individuals in their typical level of expression of all three immune genes examined, after other measured sources of variation had been taken into account. Furthermore, for two of these genes, they found that individuals that responded to changing circumstances by increasing expression levels of one had a correlated increase in expression levels of the other.

One of the joint first authors of the study, Dr Klara Wanelik, said: "Working with natural populations can be messy but it’s worth it! The environment experienced by free-living voles is much more similar to our own than that of a mouse in a laboratory. So even though a field vole may look very different from us, it actually has a lot more in common with us than we may think.

“We hope that our work will encourage people to view the immune system from a different perspective, and discourage them from ignoring immunological variation among individuals in future studies of parasite and disease risk in the wild.

“It is also important to monitor such wildlife populations as they can be a source of zoonoses (infections that can transmit from animals to humans)."

This research was supported by grants from the Natural Environment Research Council and was conducted in Kielder Forest with permission from the Forestry Commission.

The full paper, ‘From the animal house to the field: Are there consistent individual differences in immunological profile in wild populations of field voles’, can be found here.