“…Nevertheless, the number of studies that focus on the application of cytokine genes as molecular adjuvants in fish is limited when compared to those undertaken in mammals [21]. To date, it has been reported that fish cytokines such as IL-6 [22], IL-8 [23][24][25], IL-2 [24,26], IL-1β [24,25,27], IL-15, IL-17 [24], TNFα, granulocyte colony-stimulating factors (G-CSF) [25], IL12 [28], chemokine (C-C motif) ligand 3 (CCL3), CCL4, CCL19, CCL21 [29], and IFNγ [30] can be applied as promising molecular adjuvants for DNA or recombinant subunit vaccines against particular viral or bacterial infections. Interleukin-34 (IL-34), a cytokine newly discovered in 2008, has been documented as a pluripotent cytokine that modulates a wide array of cellular processes, including differentiation, adhesion, proliferation, survival, metabolism, inflammation, and immune modulators in mammals [31].…”