Morphometric parameters of blood lymphocytes in American mink (Neogale vison) selected for tameness and defensive aggression toward humans

Although there is some evidence to suggest that there is a link between behavior and immune parameters in animals, this issue is still not well understood. In particular, there is a lack of understanding of how specific behaviors affect the size of immune cells. To address this issue, we investigated the relationship between behavior and the morphometric parameters of lymphocytes in American mink (Neogale vison) that have been selectively bred for aggression and tameness toward humans at the Institute of Cytology and Genetics in Novosibirsk, Russia, for 37 years. Minks with high ("-3") and medium ("-2") aggressiveness, moderate ("+ 3") and high tameness ("+ 6"), as well as those not affected by special behavior selection, were compared with each other. We found that aggressive and tame mink significantly differed in lymphocyte size, cytoplasm content and nucleus to cell ratio (NCR). The lymphocytes of tame mink were characterized by larger size, increased cytoplasm content and lower NCR compared to those of aggressive mink and unselected mink. Among the studied parameters, the largest differences were found in the size of lymphocytes between "+ 3" and unselected minks (p = 0.000018) and in the cytoplasm content between "+ 6" and unselected minks (p = 0.000039). Minks with similar behavior ("-3" and "-2", "+ 3" and "+ 6") showed no significant differences. Our data, combined with the strong correlation reported by other researchers between morphological characteristics of lymphocytes and cytokine levels indicates that selection for specific behaviors may lead to a rebalancing in the immune system.