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C-type lectins (CTLs) are crucial innate pattern recognition receptors (PRRs) which appear throughout the animal kingdom, from nematodes and insects up to the higher animals and humans. They recognize various host and foreign carbohydrates, as well as further polypeptide and crystal ligands, evoke regulatory signals and participate in phagocytosis and priming of adaptive immune responses against viral, bacterial, fungal and parasitic infections. In the first chapter of this thesis, general concepts regarding the immune system and specifically the role of relevant PRR families, such as the CTLs, Toll-like and NOD-like receptors, are introduced. Following, the state of research concerning CTLs in veterinary medicine is summarized. Though barely nascent, veterinary glycoimmunology already presents most promising concepts and methods, featuring the role of CTLs in controlling autoimmunity, host-pathogen interactions, and cancer. The detrimental effects of CTLs, such as their causative role in allergies and the immune compromising aspect of several CTLs posing as pathogen adhesion molecules, are also reviewed. Current problems and limitations of veterinary CTLrelated research are discussed. Specifically, the limited applicability of mouse models in research on veterinary species, and deficits in species-specific characterization of CTL ligand preferences and the respective CTL-mediated signaling are addressed. A novel sheep CTL fusion protein library providing a means to study sheep CTL/ligand interactions in vitro is introduced in the second chapter. It is comprised of eight distinct recombinant CTLs, all of which were produced in suspended Chinese hamster ovary (CHO) cells, expressed as homodimers fused to the human immunoglobulin G1 fragment of crystallization (IgG1 Fc). The functionality of the sheep CTL hFc-fusion protein library was verified with known ligands of corresponding mouse CTL orthologues in ELISA- and flow cytometry-based binding studies. The obtained results indicate that similar (Dectin-1, Dectin-2, Mincle, DNGR-1) as well as differing (Langerin) ligand preferences of orthologous sheep and mouse CTLs exist. Ensuing, the ovine CTL hFc-fusion protein library was applied in a proof-of-principle flow cytometry-based pathogen screening study with the model ruminant pathogen Mycoplasma mycoides subsp. capri. Thereby, novel interactions of several sheep CTLs, such as MCL, MICL, and DCIR, were identified. In addition, an Aedes aegypti mosquito CTL hFc-fusion protein library was generated for collaborative studies on zoonotic arboviruses, such as the Rift Valley Fever virus. Finally, the generation of ovine CTL-expressing reporter cells was initiated to investigate the signal transducing potential of the respective CTL/ligand interactions. Results obtained with ovine follicle stimulating hormone isoform 3 (FSHR3) and derivative sheep Dectin-1 FSHR3 hybrid receptor reporter cell are, however, yet preliminary and require further studies.