Changes in M-CSF-like activity during chicken embryonic development

Serum cytokine profile of neonatal broiler chickens infected with Salmonella Typhimurium

The avian immune system responds to Salmonella infection by expressing cytokines and chemokines. We hypothesized that the immune status of Salmonella Typhimurium (ST) challenged neonatal broilers would differ from the uninfected treatment. The objective of this experiment was to evaluate 12 cytokines. Day of hatch male chicks were randomly allocated into a control or ST challenged group. At day three of age, sterile diluent or 5.0 × 108 CFU of ST was given orally to each chick. Blood was obtained 24 h post challenge and serum separated for later analysis (n = 30 chicks/treatment). Significant (p ≤ 0.05) increases in pro-inflammatory cytokines-interleukin-6 (IL-6), IL-16, and IL-21; anti-inflammatory cytokines- IL-10; chemokines-regulated on activation, normal T cell expressed and secreted (RANTES), macrophage inflammatory protein-1β (MIP-1β), and MIP-3α; colony stimulating factors-macrophage colony-stimulating factor (M-CSF); and growth factors-vascular endothelial growth factor (VEGF) were observed in the serum of the challenged chicks when compared to the control. No significant differences were observed in IL-2, interferon gamma (IFNγ), and IFNα. These data indicate the detection of mucosal immune responses in broiler chickens following ST infection. The heightened levels of pro-inflammatory cytokines, chemokines, and colony stimulating factors align with known inflammatory mechanisms, like the influx of immune cells. However, the elevation of IL-10 was unexpected, due to its immunoregulatory properties. Notably, the rise in VEGF levels is compelling, as it suggests the possibility of tissue repair and angiogenesis in ST infected birds.

Control of CSF-1 induced inflammation in teleost fish by a soluble form of the CSF-1 receptor

The colony-stimulating factor-1 (CSF-1) is the principal regulator of the survival, proliferation, differentiation, and function of macrophages and their precursors, and has been shown to play a role in the etiology of inflammation. We recently identified a novel mechanism for the control of CSF-1 activity in teleost fish, through the production of an inhibitory soluble form of the CSF-1 receptor (sCSF-1R). Primary goldfish kidney macrophages selectively expressed sCSF-1R during the senescence phase, which corresponds to a defined stage of in vitro culture development where inhibition of macrophage proliferation and apoptotic cell death are prominent. In contrast, primary macrophage cultures undergoing active proliferation displayed low levels of sCSF-1R expression. Addition of purified recombinant sCSF-1R to developing primary macrophage cultures leads to a dose-dependent decrease in macrophage proliferation and inhibits macrophage antimicrobial functions including chemotaxis, phagocytosis, and production of reactive oxygen intermediates. Using a goldfish in vivo model of self-resolving peritonitis, we found that sCSF-1R plays a role in the inhibition of inflammation, following an initial acute phase of antimicrobial responses within an inflammatory site. Soluble CSF-1R inhibits pro-inflammatory cytokine production, inhibits leukocyte recruitment to the inflammatory site and decreases ROS production in a dose-dependent manner. This sCSF-1R-dependent regulation of inflammation appears to be an elegant mechanism for the control of macrophage numbers at inflammatory sites of lower vertebrates. Overall, our results provide new insights into the evolutionary origins of the CSF-1 immune regulatory axis.

Development of macrophages of cyprinid fish

The innate immune responses of early vertebrates, such as bony fishes, play a central role in host defence against infectious diseases and one of the most important effector cells of innate immunity are macrophages. In order for macrophages to be effective in host defence they must be present at all times in the tissues of their host and importantly, the host must be capable of rapidly increasing macrophage numbers during times of need. Hematopoiesis is a process of formation and development of mature blood cells, including macrophages. Hematopoiesis is controlled by soluble factors known as cytokines, that influence changes in transcription factors within the target cells, resulting in cell fate changes and the final development of specific effector cells. The processes involved in macrophage development have been largely derived from mammalian model organisms. However, recent advancements have been made in the understanding of macrophage development in bony fish, a group of organisms that rely heavily on their innate immune defences. Our understanding of the growth factors involved in teleost macrophage development, as well as the receptors and regulatory mechanisms in place to control them has increased substantially. Furthermore, model organisms such as the zebrafish have emerged as important instruments in furthering our understanding of the transcriptional control of cell development in fish as well as in mammals. This review highlights the recent advancements in our understanding of teleost macrophage development. We focused on the growth factors identified to be important in the regulation of macrophage development from a progenitor cell into a functional macrophage and discuss the important transcription factors that have been identified to function in teleost hematopoiesis. We also describe the findings of in vivo studies that have reinforced observations made in vitro and have greatly improved the relevance and importance of using teleost fish as model organisms for studying developmental processes.

Growth Factors of Lower Vertebrates

Colony-stimulating factor-1 (CSF-1) regulates mononuclear cell proliferation, differentiation, and survival. The functions of CSF-1 are well documented in mammals; however, little is known about CSF-1 biology in lower vertebrates. This is the first report on the identification and functional characterization of a fish CSF-1 molecule expressed highly in the spleen and in phorbol 12-myristate 13-acetate-stimulated monocytes. Goldfish CSF-1 is a 199-amino acid protein that possesses the required cysteine residues to form important intra-chain and inter-chain disulfide bonds that allow CSF-1 to form a functional homodimer and to interact with its high affinity receptor, CSF-1R. Recombinant goldfish CSF-1 formed a homodimer and bound to the soluble goldfish CSF-1R. The addition of the recombinant CSF-1 to sorted goldfish progenitor cells, monocytes, and macrophages induced the differentiation of monocytes into macrophages and the proliferation of monocyte-like cells. The proliferation of these cells was abrogated by addition of an anti-CSF-1R antibody as well as the soluble CSF-1R. The ability of the soluble CSF-1R to inhibit CSF-1-induced proliferation represents a novel mechanism for the regulation of CSF-1 function.