Ghrelin is peptide hormone/cytokine that is mainly known to regulate metabolic processes including food intake, appetite, growth and energy balance, but it also plays an essential role in immune system. To evaluate the immunomodulatory actions of ghrelin analogs in rainbow trout, primary isolated head-kidney cells were treated with rainbow trout ghrelin and its truncated analog desVRQ-ghrelin (rt-desVRQ-Ghrl ) under in vitro culture conditions and over a time-course (0, 2, 4 24 h). The mRNA levels of genes of interest relevant to pro-inflammation, chemotaxis, phagocytosis, leukocyte migration, antig en presenting process, myeloid differentiation and cytokine-JAK/STAT signaling were measured by real-time quantitative PCR. Treatment of primary cells, with these peptides, resulted in perturbations that displayed overlapping and divergent actions. The differing actions between the two ghrelin analogs, on various immune processes , and at differing time points, suggests the two analogs may have divergent roles in fish immunity . These results confirm the immunomodulatory effects of gh relin peptides, providing a better understanding of these peptides in immune system of rainbow trout.