Department of Organismal Biology

Söderhäll Lab: </br>Invertebrate immune reactions

We are investigating innate immune reactions in invertebrates and compare these reactions with those present in higher animals (vertebrates). One example is melanization; a reaction that is present in virtually all organisms, but detailed studies on this reaction is mainly performed in crayfish/crustaceans and a few insects. Melanization is an important defence response and the products of this reaction are functioning as antimicrobial peptides and several proteins of the so called proPO-cascade are activated and perform important biological functions. Activation of the proPO-system is carried out by miniuscle amounts of microbial polysaccharides present in the blood of the host animal. The control and regulation of this protease cascade is also studied.

Blood cell formation

We study how development of blood cells (hemocyte) is regulated at the molecular level, and further examine relationships between the hematopoietic tissue and the neuronal precursor lineage that produces adult-born neurons in the brain of freshwater crayfish. We have discovered a group of cytokines, astakines, involved in both these processes and now focus on: 1) finding specific markers for hematopoietic and neurogenic precursor cells 2) how astakines affects stem cells to become mature hemocytes and 3) how the hematopoietic system and adult neurogenesis are coordinately regulated. We hope to get increased knowledge about the regulation of hematopoiesis, neurogenesis and the evolution of cytokines.

Immuno-Neuro interactions

The relationship between the nervous and immune systems in crayfish is studied. Mature circulating hemocytes of crayfish are originating from the hematopoietic stem cells located in the hematopoietic tissue (HPT). However, no mature hemocytes can be found within the hematopoietic cell lobules and only few cells in the circulatory system have a stem cell morphology as in HPT. These cells are released from the HPT before they are mature and their final differentiation and maturation take place outside the HPT in the circulation. We are investigating how the peripheral nervous system is involved in the final differentiation of hemocytes in crayfish.

Dopamine, a hormone and neurotransmitter, is involved in neurogenesis in vertebrates and a substrate for phenoloxidase (PO), an important immune protein that catalyze the melanization reaction and is similar to vertebrate tyrosinases. How PO participates in crayfish neurogenesis by for example regulating the dopamine level is studied.