Signaling pathways derived from TLRs are very complex. parameters of blood, secretion of antioxidant enzymes, expression of Toll-like receptors, mechanisms of immune response, as well as the expression and activity of cyclooxygenases. We emphasize the interrelations between the parasite and the host at the cellular level resulting from the direct impact of the parasite as well as host defense reactions that lead to changes in the hosts tissues and organs. family cestodes, in the liver results in pressure and disturbances in the proper functioning of this organ. Finally, different metabolites secreted by parasites may also affect the functioning of the host organism. Proteolytic enzymes, including acetylcholine and histamine secreted by and cause inflammation, inhibition of blood coagulation and dilation of blood vessels [2,3,4,5]. The interactions between the parasite and the host have an effect on the immune response of the host. Occasionally, there is an excessive and inadequately directed host defense response leading to the degradation of its tissues and organs [2,6]. The immunopathological reactions result in changes in the host organism, including enlargement of internal organs (spleen, liver, lymph nodes) due to the increased activity of immune cells (macrophages and lymphocytes), inflammatory lesions and foci in the liver (cysts, abscesses, granulomas), immune complexes in the kidneys, and the anaphylactic reaction and shock [7,8,9]. WASF1 Parasitic infections activate all kinds of non-specific (innate) and specific (acquired) immune responses, the latter consisting of cellular and humoral components. A specific response develops during the first contact Hydroxyurea with the parasite and its antigens, followed by the stimulation of T helper cells and B lymphocytes for the production of antibodies [10]. In turn, the non-specific response is related to the occurrence of natural physico-mechanical (maintaining tissue continuity), biological (secretion of lysozyme, lactoferrin) and chemical barriers (low pH of the skin and stomach) of the host Hydroxyurea organism. However, the most characteristic phenomenon determining the non-specific response is phagocytosis, which occurs through macrophages, neutrophils, eosinophils and components of the complement system in the environment of reactive oxygen and nitrogen. A parasitic invasion triggers a humoral immune response involving the production of immunoglobulins, the control of extracellular parasites present in the blood and in bodily fluids, as well as a cellular response associated with the removal of intracellular parasites [6]. The biochemical, histochemical, and pathophysiological aspects of the parasiteChost mutual relationship using various experimental models have been the subject of many studies [11,12,13,14]. However, the molecular mechanisms of these interactions are still not fully understood. In the present work, we show the biochemical and molecular mechanisms of parasiteChost interaction based on the recent research on the rat tapeworm Rudolphi, 1819 The rat tapeworm (Cestoda) is an intestinal parasite of small rodents, including mice and rats. Humans are only accidental hosts [15,16,17,18,19,20]. The strobila of a mature tapeworm can reach 20 cm to 60 cm in length and 3 mm to 5 mm in width. It contains from 800 to 1000 proglottids, which are 3.5 mm wide and 0.76 mm long. The length of the tapeworm depends on the intensity of infection (crowding effect) [21,22,23,24]. The scolex of has no hooks but is equipped with four suction cups. The tapeworms eggs are oval, from 60 to 85 m in diameter, devoid of polar filaments in the inner shell [17,25,26]. The life cycle of requires an intermediate arthropod host, including mealworms (reaches maturity within 18 to 20 days, after which the gravid proglottids filled with eggs are excreted with the hosts feces [17,25,26]. The symptoms of hymenolepidosis (or hymenolepiasis) in humans are not very characteristic and are limited to indigestion, abdominal pain, and diarrhea, but most commonly the infection is asymptomatic [16,30,31,32,33,34]. Although an adult tapeworm does not have hooks in its structure that could damage host tissues, its metabolites may affect Hydroxyurea the functioning of the gastrointestinal tract by, inter alia, increasing the secretion of saliva, inhibiting the secretory capacity of the stomach, as well as increasing the activity of trypsin in the duodenum [35]. Rats are most commonly used in studies on hymenolepidosis. Hydroxyurea Mice are not a very suitable research model, as their immune system exhibits increased activity already during the first invasion. Research shows that at the first experimental infection of mice, after about two weeks, the development of this parasite is halted; reinfection results in its spontaneous and total expulsion. The rat immune system does.