The effect of milk thistle (Silybum marianum) on the state of T- and B-cell immunity and natural resistance of the immune system of two-year-old carp

Purpose. To investigate the effect of the supplementation of the basic diet of age-2 carp with different amounts of milk thistle (Silybum marianum) seeds on the state of T- and B-cell immunity and indicators of the natural resistance of their organism. Methodology. The experimental part of the work was performed at the Lviv Research Station of the Institute of Fisheries NAAS. The study was conducted using three groups of age-2 Lubin scaly carp, which were reared under conditions of analogue ponds for 60 days of the culture season. The material for the study was fish blood, which was sampled at the end of the experiment. The numbers of T- and B-lymphocytes and their functional activity in the heparin-stabilized blood were determined using the rosette test. Phagocytosis parameters of granulocytes were evaluated by phagocytic activity (FA), phagocytic number (FN) and phagocytic index (FI). Lysozyme activity of serum (LAS) was determined by the response to the microbic test culture of Micrococcus lysodeikticus using the photonephelometric method. When determining the bactericidal activity of blood serum, Aeromonas hydrophila was used as a test microbe. Findings. The supplementation of the diet of age-2 carp with milk thistle seeds at an amount of 5% resulted in a decrease in the number of T-lymphocytes (common, active and theophylline-resistant) and caused immunosuppressive effects on their functional activity due to the redistribution of the receptor apparatus of immunocompetent cells. In particular, an increase in the number of functionally inactive T-lymphocytes and reduction of the proportion of cells with medium and high density of receptors were observed. At the same time, when using this plant supplement at an amount of 1% in the blood of carp, a tendency to an increase in the number of these populations of T-lymphocytes and an increase in their functional activity were observed. At the same time, carp of both experimental groups, compared to the control, had the number of high-grade B-lymphocytes increased (p <0.05). These data indicate the dose-dependent effect of the milk thistle supplement on the state of the T- and B-cell system of the specific protection of the fish body. The stimulatory effect of the studied supplement on the activity of the cellular and humoral components of age-2 carp resistance was found. This was evidenced by higher bactericidal, lysozyme and phagocytic activities in the blood of experimental groups compared to the control. This effect was expressed to a greater extent in carp, the basic diet of which was supplemented with 1% of milk thistle. Originality. For the first time, the effect of milk thistle on the activity of T- and B-cell immunity and non-specific resistance of the body of age-2 carp have been investigated. Practical value. Supplementation of the carp feeds with milk thistle in the process of commercial carp rearing allows increasing the natural resistance of their organism.