Group Uli Theopold

Our group is interested in innate immune reactions in insects. Immunity in humans comprises both reactions, which can change during an individual’s life (adaptive immunity) and reactions that occur in a more stereotypic way each time we encounter an infectious agent (innate immunity). In a way, adaptive immunity can be described as the immune memory of the individual whereas innate immunity is the evolutionary memory of the species or population. Insects are perfect model systems to study innate immunity. We use primarily two model insects: a lepidopteran species (Galleria mellonella) and the vinegar fly (Drosophila melanogaster), which is one of the best established model systems in biology. At present our focus is on the following projects.

Coagulation of insect hemolymph

Arthropods with their open circulatory systems seal wounds and keep bacteria from entering the hemocoel using efficient clotting systems. Until some years ago little was known about the molecular basis for clotting of insect hemolymph. We have established a number of methods to study this reaction in Drosophila melanogaster. Using these methods, we could show that during Drosophila clotting, extracellular webs are formed, which immobilize bacteria and prevent their dissemination into the hemocoel (Fig.1). In addition, proteomics studies allowed us to identify several proteins involved in this reaction. Mutants in the genes encoding these proteins show immune defects. Our results contribute to a more complete picture of the function and evolution of innate immunity. In collaboration with Dr. Heiko Herwald (Lund University) we study which implications our findings have for the human immune system. To challenge the fly’s immune system we use different methods including infection with entomopathogenic nematodes, which has been established by Dr. Pavel Hyrsl (Masaryk University, Czech Republic) with whom we are also collaborating.

Fig.1: left: a Drosophila hemolymph sample turns viscous after bleeding. right: in the hemolymph clot, fibers can be stained with lectins (upper part) in which bacteria are captured (lower part, the bacteria are labeled with green fluorescent protein).

 

 

The immune response against tumors

In a different project we study how the innate immune reacts against tumors. For this we also use the fly Drosophila melanogaster as a model system. There are a number of mutant fly strains, which develop tumors but we can also induce tumor formation genetically. We find that both natural and induced tumors induce immune responses and we are now trying to understand how much these responses contribute to controlling tumor growth.

Read more about Group Uli Theopold at home department web site