VIP and systemic lupus erythematosus: In contrast, protein expression studies revealed a mild (though not statistically significant) increase in PACAP protein levels in SLE mice of both age groups (p > 0.05 vs. WTs; Figure 2F,G), paralleled by a robust increase in the expression of VIP in 7 mo NZBWF1 mice (** p ≤ 0.01 vs. 7 mo WTs; Figure 2H).