Immune modulation by fish kinetoplastid parasites : a role for nitric oxide

Trypanoplasma borreli and Trypanosoma carassii are kinetoplastid parasites infecting cyprinid fish. We investigated the role of nitric oxide (NO) in immune modulation during T. borreli and T. carassii infection of carp. Phagocytic cells from different organs produced NO and serum nitrate levels increased, demonstrating that T. borreli activates NO production in vivo. In contrast, T. carassii did not induce NO production in vivo and inhibited LPS-induced NO production in vitro. Production of NO was detrimental to the host as T. borreli-infected carp treated with the inducible NO synthase inhibitor aminoguanidine had a higher survival than infected control carp. This detrimental effect can be explained (in part) by the toxicity of NO to cells in vitro as NO inhibited the proliferative response of blood and spleen leukocytes. Head-kidney phagocytes were resistant to the immunosuppressive effects of NO in vitro. The NO-inducing activity of T. borreli may be an adaptation developed to ensure survival and immune evasion in the fish host. Apparently, T. carassii has adopted another strategy by deactivating specific functions of phagocytes. Both strategies may ensure long-term survival of the parasite

Antibiotica, een vloek of een zegen?

In Aquacultuur 2010, nr. 5 stond op pagina 33 van het artikel "Aan tafel bij Sietze Leenstra" de opmerking, dat antibiotica het immuunsysteem verstoren. Hier is wel iets voor te zeggen, maar toch moeten we oppassen, dat we niet alle antibiotica op één hoop smijten. Volgens de auteur is het vooral het gebruik van oxytetracycline in de aquacultuur, waar we een vraagteken bij moeten plaatsen

T cells and the humoral immune system

Lymphoid cells and macrophages play an important role in the development and rnaintance of humoral and cellular immunity in mammals. The lymphoid cells in the peripheral lymphoid organs are divided into two major classes: (1) thymus-derived lymphocytes or T cells and (2) bursa-equivalent-derived lymphocytes or B cells. Humoral immune responses to most antigens require interaction between macrophages, T cells and B cells. Antigen-stimulated T cells do not produce antibodies but secrete regulatory substances which have a stimulating or a suppressive effect on the differentiation of antigenstimulated B cells into antibody-producing plasma cells. The macrophage plays an important role in this T-B interaction by concentrating the antigen by endocytosis and presenting a part of it in a persisting immunogenic form on its cell membrane. Several aspects of the regulatory influence of the T cell on the humoral (B) immune system were investigated in our laboratory and the results of our experiments are presented in the papers added to this thesis

The potential for crop rotation in controlling diseases in shrimp culture

The use of antibiotics and other chemicals in controlling shrimp pathogens become ineffective as the strains grow more resistant to these chemicals. Moreover, the bacterial pathogen (Vibrio harveyi) produced biofilm coating that protects it from dying and disinfection procedures that are followed during pond preparation. Biological control is being considered as an alternative means of preventing shrimp disease outbreak. The main principle behind biological control is to enhance the growth of beneficial microorganisms which serve as antagonists or target pathogens. The paper discusses shrimp and tilapia crop rotation as a form of effective biological control, a technique which is already being practiced in Indonesia and the Philippines

The ontogeny of mucosal immune cells in common carp (Cyprinus carpio L.)

The ontogeny of carp (Cyprinus carpio L.) immune cells was studied in mucosal organs (intestine, gills and skin) using the monoclonal antibodies WCL38 (intraepithelial lymphocytes), WCL15 (monocytes/macrophages) and WCI12 (B cells). In addition, recombination activating gene 1 expression was examined in the intestine with real time quantitative PCR and in situ hybridization to investigate extrathymic generation of lymphocytes. WCL38+ intraepithelial lymphocytes (putative T cells) appeared in the intestine at 3 days post-fertilization (dpf), which is shortly after hatching but before feeding, implying an important function at early age. These lymphoid cells appear in the intestine before the observation of the first thymocytes at 3¿4 dpf, and together with the expression of recombination activating gene 1 in the intestine, suggests that similar to mammals at least part of these cells are generated in the intestine. WCL15+ monocytes/macrophages appeared in the lamina propria of the intestine at 7 dpf, but considerably later in the epithelium, while WCI12+ (B) cells appeared in intestine and gills at 6¿7 weeks. From these results it can be concluded that putative T cells occur much earlier than B cells, and that B cells appear much later in the mucosae than in other internal lymphoid organs (2 wpf)

The immune system: effects of water temperature and acidification

This chapter provides a general overview of the defence mechanisms in fish, its interactions with the neuroendocrine system and the influence of environmental factors such as water temperature and acidification on its function