Distinct immune-and defense-related molecular fingerprints in sepatated coelomocyte subsets of Eisenia andrei earthworms

During phylogenesis different types of immunocytes such as amoebocytes and eleocytes have developed in earthworms to defend the host against microbial pathogens. Previously we applied a cell sorting-based approach to untangle the morphological and functional properties of these aforementioned coelomocyte subsets. In order to compare their constitutive gene expression patterns, cell-sorting was performed and followed by semiquantitative RT-PCR in the distinct, separated coelomocyte subpopulations of unmanipulated Eisenia andrei earthworms. We targeted a variety of genes with diverse functions ranging from pattern recognition through intracellular signaling to oxidative stress. Several immune-related genes (CCF, TLR, lumbricin, LuRP, MyD88) were only manifested in the amoebocytes. In contrast, other immune response genes (lysozyme, lysenin), lysosomal hydrolases (cathepsin L and cathepsin C) and cystatin B were expressed in both subpopulations. In addition, cell signaling molecules (MyD88, PKC1) and oxidative stress-related genes (Cu/ZnSOD, MnSOD) were mainly observed in amoebocytes, while other stress-related genes (Cd-metallothionein, catalase) were apparent in both subsets. We conclude that these characteristic differences of the molecular signatures manifest in the functional heterogeneity of distinct coelomocyte subtypes.