Wi Immunologists
Tom Little

The work of my lab is on the genetics and evolution of parasitic interactions. We use the crustacean Daphnia for this purpose, with the goal of linking patterns of genomic variability and immune responses to epidemiological and evolutionary dynamics in the field.

Specifically, our work on Daphnia examines

1) How the
immune response is linked to parasite resistance and, ultimately, to host and parasite fitness. One of our aims to is understand variation in immune response magnitude in a world of diverse parasites, coinfection, maternal effects, senescencing hosts and environmental variability. This work is our main contribution to the Wild Evolution initiative. With Daphnia, we have the capacity to study immune responses under more realistic, real-world conditions at both the genetic and cellular level. Daphnia were the subject of pioneering work on invertebrate cellular immunology, and this area has recently been reborn in my lab. We also use large-scale transcriptomics (via illumina sequencing technology) to identify genes that are up- or down-regulated in response to pathogen invasion.

2) The genes and genomic regions subject to parasite mediated selection. We are currently embarking on new
population genomic work to characterise signatures of selection across multiple entire genomes. For the interaction between D. magna and its dominant pathogen, P. ramosa, there is an exceptionally deep history of experiments on susceptibility which has revealed extensive genetic variation in both host and pathogen, including strong genotype by environment interactions and genetic specificity. It is not known, however, which genes are involved. Conversely, the effects of natural selection via coevolutionary interactions on genes and genomes have not been widely documented in any organism. Population genomics can be used to address this. Until very recently, genomes were sequenced and the gathering of polymorphism data was restricted to, for example, the study of candidate genes. But technological and cost barriers have now fallen to as little £1000 per genome, which is simply remarkable.

The Little Lab

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