Purpose of research. To evaluate the effect of LAC (mononuclear blood leukocytes activated by IL-2 ex vivo) suspension infusion on clinical, biochemical, hematological and immunological characteristics of a healthy Beagle dog to assess the safety of the product’s application. Materials and methods. The research object is a 6-year Beagle dog male. The LAC suspension in Hank’s solution has been infused intravenously with a low rate of administration; the dose used was 25 m cells in 5 ml. An autologous culture of LAC has been generated from canine blood, evaluated by morphology, phenotype, and target activity in Laboratory of Cell Immunity by FBSI «N.N. Blokhin National Medical Research Center of Oncology». Results. The analysis of hematological, immunological and radiological characteristics of the object has identified no signs of any pathology development. That turns to conclusion that the given LAC medication dose’s local, hematological and systemic toxicity is low or absent. Conclusions. Data received within the research may be of interest to human medicine as well as to veterinary medicine as it could be considered a part of pre-clinical trials of the LAC suspension, which effectiveness has already been confirmed in human clinical oncology, and also as a safety assessment of even more complex constructs based on activated immunocompetent cells that are still under development. The study can serve as a basis for the development of activated leukocytes-based cellular anticancer immunotherapy (LAC, immune checkpoint molecules and SAR), primarily its toxicity studying models, and also be a part of pre-clinical studies of LAC toxicity.