Interleukin 4 increases CCR9 expression and homing of lymphocytes to gut-associated lymphoid tissue in chickens

The effects of in vitro and in vivo IL-4 supplementation on thymocyte and splenocyte CCR9 mRNA amount and migration were studied. Thymocytes, splenocytes, splenocytes + thymocytes (2:1), and splenocytes + bursocyte cells (2:1) were supplemented with either 0 or 5 ng/ml IL-4 for 5 d. CCR9 mRNA was undetectable in all experimental groups supplemented with 0 ng/ml IL-4. IL-4 treatment (5 ng/ml) upregulated (P = 0.01) CCR9 mRNA only in the splenocyte + thymocyte cell culture. IL-4-mediated CCR9 mRNA induction in the splenocyte + thymocyte cell culture was dependent on the in vitro dose of IL-4 supplementation. IL-4-treated splenocyte + thymocyte cells when injected in vivo preferentially migrated to cecal tonsils. In vivo supplementation of IL-4 was achieved through in ovo injection of recombinant chicken IL-4 plasmid. Cecal tonsils in chicks hatched from IL-4-plasmid-injected eggs weighed more, had a higher amount of CCR9 mRNA, and had a higher percentage of CD8+ cells than cecal tonsils from chicks hatched from PBS-injected eggs. It could be concluded that IL-4 induces CCR9 mRNA in thymocytes and splenocytes and directs the migration of cells to gut-associated lymphoid tissue.