An increasing body of research implicates inflammatory processes, including alterations in the neutrophil-lymphocyte ratio (NLR), in the pathophysiology of psychiatric illness. The deer mouse (Peromyscus maniculatus bairdii) is commonly studied for its naturalistic expression of compulsive-like behaviour. Towards future efforts to gain an understanding of how innate and adaptive immune processes might be involved this model, we set out to study the effects of pegfilgrastim, a pegylated recombinant human granulocyte colony-stimulating factor (g-CSF) analogue, on the NLR of both male and female deer mice. Briefly, 54 deer mice (equally distributed between sexes) were exposed to a single injection with either control or pegfilgrastim (0.1 or 1 mg/kg) ( n = 18 per group). Six mice of each group were euthanized on days two, four and seven post-administration, blood collected and the NLR calculated. Our results showed that irrespective of dose, pegfilgrastim resulted in higher NLR values in mice of both sexes at days four and seven of testing, but that female mice exposed to the higher dose, presented with significantly higher NLR values irrespective of time, compared to male mice exposed to the same. These data highlight important dose and sex-specific areas for consideration and provide a useful basis for further study of both immunological and brain-immune crosstalk processes in deer mice.

An increasing body of research implicates inflammatory processes, including alterations in the neutrophil-lymphocyte ratio (NLR), in the pathophysiology of psychiatric illness. The deer mouse (Peromyscus maniculatus bairdii) is commonly studied for its naturalistic expression of compulsive-like behaviour. Towards future efforts to gain an understanding of how innate and adaptive immune processes might be involved this model, we set out to study the effects of pegfilgrastim, a pegylated recombinant human granulocyte colony-stimulating factor (g-CSF) analogue, on the NLR of both male and female deer mice. Briefly, 54 deer mice (equally distributed between sexes) were exposed to a single injection with either control or pegfilgrastim (0.1 or 1 mg/kg) (n = 18 per group). Six mice of each group were euthanized on days two, four and seven post-administration, blood collected and the NLR calculated. Our results showed that irrespective of dose, pegfilgrastim resulted in higher NLR values in mice of both sexes at days four and seven of testing, but that female mice exposed to the higher dose, presented with significantly higher NLR values irrespective of time, compared to male mice exposed to the same. These data highlight important dose and sex-specific areas for consideration and provide a useful basis for further study of both immunological and brain-immune crosstalk processes in deer mice.