Do fish thrombocytes play an immunological role? Their cytoenzymatic profiles and function during an accidental piscine candidiasis in aquarium

Fish (F) thrombocytes (THRs) from healthy trouts were studied in terms of cytoenzyme expression. FTHRs were positive to acid periodic of shiff (PAS) and acid phosphatase (ac. phos.) without tartaric acid (-TA) stainings, as well to alkaline phosphatase. However, when compared with autologous macrophages (MOs), they were negative to naphthol cloroacetate esterase (AS-D), alpha-naphthyl acetate esterase (Anae), peroxidase (perox) and control ac. phos. with tartaric acid (+TA) stainings, thus indicating a lack of typical lysosomial enzymes. This evidence supports the notion that FTHRs are not true digesting cells. Quite interestingly, trouts and human MOs were positive for PAS, AS-D, Anae, and perox stainings, thus confirming that cellular cytochemistries are maintained across evolution as their phagocytic functions. Additionally, blood films from trouts, accidentally infected with Candida albicans in aquarium, were morphologically analyzed. Actually, FTHRs interact with erythrocytes, potentiating the formation of rosettes around a central MO. Polymorph nuclear cells and lymphocytes are present in these cellular aggregates, thus suggesting that FTHRs may represent a link between innate and adaptive immunity

Maturation of fish erythrocytes coincides with changes in their morphology, enhanced ability to interact with Candida albicans and release of cytokine-like factors active upon autologous macrophages

Erythrocytes from the rainbow trout Salmo gairdneri Richardson (Salmo g.R.) were classified into immature and mature populations, respectively, by measuring longitudinal diameters. More elongated fish erythrocytes (FE), classified as mature cells, were those interacting with Candida albicans (CA) in a higher frequency in terms of either binding to the fungus or its intracellular engulfment. At the same time, in the rosetting phenomenon more elongated mature FE surrounded macrophages (Mcircle divide) phagocytosing CA. Finally, FE activated by CA released in the supernatants cytokine-like factors able to modulate Mcircle divide functions. In particular, these active supernatants were analyzed for their capacity to inhibit Mcircle divide migration Macrophage Inhibition Factor (MIF) activity and enhance Mcircle divide phagocytosis. Both activities were detected in supernatants from CA stimulated FE but not in control supernatants. MIF activity could play a role in the accumulation of Mcircle divide in the context of functional rosettes, while the factor enhancing Mcircle divide phagocytosis could promote clearance of CA in a more efficacious way

Antigenically-activated avian erythrocytes release cytokine-like factors: a conserved phylogenetic function discovered in fish

Fish erythrocytes (FE) are endowed with the ability to produce cytokine like factors when stimulated with Candida albicans (Ca). In order to evaluate whether similar activities are still conserved in bird erythrocytes (BE), a morphological, cytochemical and immunological evaluation was conducted on peripheral cells in chickens (Gallus gallus). BE form rosettes with monocytes (Mo)-macrophages (MØ), and Mo-MØ according to cytochemical analysis maintain phagocytic functions across the evolution. Finally, Ca-activated BE release in the supernatants cytokine like-factors which enhance Mo-MØ phagocytosis (interferon-γ like activity) and inhibit Mo-MØ migration in agarose (Migration inhibitory factor activity). In conclusion, bird erythrocytes, as non immune cells, are able to participate in the immune response contributing to the host defence