were assessed throughout (Hart, 1991) . No changes in overt sickness behaviors were observed 143 for any experiment (data not shown). 
( Figure 1D ).
The third method we employed was that developed by Vandesompele 215 were found to be the most stable genes with the lowest expression stability values ( Figure 1F ).
However, NormFinder resulted in rplp0 having the lowest stability value of 0.326, indicating that 217 the model-based approach identified rplp0 as the most stable gene.
Together, these methods identified the two most stable candidate housekeeping genes 219 as hprt1 and rplp0. We calculated the geometric mean of the Cq values from hprt1 and rplp0 to 220 be used in the 2 -DDCq method for calculations of relative expression for our target genes. 
Baseline sex differences in relative gene expression (qPCR) were assessed by 238 evaluating the male and female saline-treated groups. To directly compare these two groups in 239 the PCR analysis, the male saline-treated group was normalized to the female saline-treated 240 group and analyzed using independent, two-sample t-tests.
To analyze changes in relative gene expression (qPCR) across the 24-hour time course,
we normalized each group to their respective same-sex saline-treated group and used two-way B. C. 
Female Male Relative Gene Expression Relative Gene Expression Relative Gene Expression 
Relative Gene Expression 
Relative Gene Expression 
Female Male Protein Concentration (pg/mg tissue) Notably, the peak il-1a and il-1b expression in males was roughly 3-fold higher than that of the 381 peak female expression for these cytokines, and the il-6 peak expression in males was more 382 than 10-fold higher than that of females ( Figures 3C2, 3D2 , and 3E2). showed significantly higher expression of ifng at baseline than did males (see Figure 3Q ). 
Importantly, these data largely overlap with the timing and patterns of response seen in the 486 same genes measured using relative mRNA expression (see Figures 5A and 5B ). A.
B.
Here 
The interferon family of cytokines showed a sex-specific pattern of expression in the 586 hippocampus. Specifically, males showed increases in IFNa, IFNb, and IFNg, but females only 587 showed a significant response in IFNb. This is consistent with previous findings that showed 588 females increased gene expression of IFNb, but not IFNa, in response to peripheral poly I:C, 589 though this study did not measure these effects in males for comparison (Murray et al., 2015) . A.
B.