This study presents a comprehensive comprehensive investigation of the specific biological activity and safety profile of "Bursanatal," a novel tissue-based drug derived from the bursa of Fabricius, positioned as a potent corrector of the humoral and cellular immune responses. In the first phase of the research, the drug's protective efficacy was verified using lethal and sub-lethal models of experimental salmonellosis (Salmonella typhimurium and Salmonella enteritidis), demonstrating a statistically significant increase in the survival index (by 20-40%) and a tenfold increase in LD50. The second phase focused on the regenerative potential of "Bursanatal" in the context of secondary immunodeficiency induced by the cytostatic agent cyclophosphamide. Through multicolor flow cytometry, it was established that the drug effectively accelerates the restoration of CD3+, CD4+, and CD22+ cell populations, normalizing the immunoregulatory index (CD4+/CD8+). Additionally, industrial trials in broiler chickens confirmed a synergistic effect with vaccines, reflected in a significant increase in antibody titers (by 2.6 log2). Comprehensive toxicological assessments, including the MTT assay on five human and animal cell lines and 30-day histopathological studies, confirmed the complete absence of cytotoxic and organotoxic effects. The cumulative results identify "Bursanatal" as a promising immunomodulatory agent capable of maintaining physiological homeostasis under conditions of critical infectious pressure and chemical immunosuppression.
