Naive and memory T cells in sheep exhibit distinct pathways of lymphocyte recirculation. Memory T cells, characterized by high expression of CD2, CD58, CD44, and CD11a, and low expression of CD45R, recirculate primarily through afferent lymph, indicating a blood-to-tissue pathway. In contrast, naive T cells, marked by low expression of these adhesion molecules and high CD45R, predominantly recirculate through efferent lymph, suggesting a blood-to-lymph node pathway. Memory T cells are long-lived and continuously recirculate between blood and lymphoid tissues, while naive T cells have a shorter lifespan and are more transient. The study used sheep as a model to investigate these differences, identifying memory and naive T cells based on surface markers and their response to recall antigens. Memory T cells showed enhanced proliferative responses to antigens, indicating their functional superiority. The distinct recirculation patterns of memory and naive T cells suggest that they use different homing receptors and migration strategies, which may optimize their interactions with antigens. The findings highlight the importance of adhesion molecules and CD45 isoforms in distinguishing these cell populations and their roles in immune surveillance and memory. The study also demonstrated that memory T cells are a dividing population, while naive T cells are predominantly non-dividing, supporting the idea that memory requires persistent antigenic stimulation. Overall, the results provide insights into the distinct recirculation and functional properties of naive and memory T cells in the immune system.Naive and memory T cells in sheep exhibit distinct pathways of lymphocyte recirculation. Memory T cells, characterized by high expression of CD2, CD58, CD44, and CD11a, and low expression of CD45R, recirculate primarily through afferent lymph, indicating a blood-to-tissue pathway. In contrast, naive T cells, marked by low expression of these adhesion molecules and high CD45R, predominantly recirculate through efferent lymph, suggesting a blood-to-lymph node pathway. Memory T cells are long-lived and continuously recirculate between blood and lymphoid tissues, while naive T cells have a shorter lifespan and are more transient. The study used sheep as a model to investigate these differences, identifying memory and naive T cells based on surface markers and their response to recall antigens. Memory T cells showed enhanced proliferative responses to antigens, indicating their functional superiority. The distinct recirculation patterns of memory and naive T cells suggest that they use different homing receptors and migration strategies, which may optimize their interactions with antigens. The findings highlight the importance of adhesion molecules and CD45 isoforms in distinguishing these cell populations and their roles in immune surveillance and memory. The study also demonstrated that memory T cells are a dividing population, while naive T cells are predominantly non-dividing, supporting the idea that memory requires persistent antigenic stimulation. Overall, the results provide insights into the distinct recirculation and functional properties of naive and memory T cells in the immune system.