Campylobacter is a bacterium that colonizes the lower gastrointestinal tract of poultry and may influence the intestinal environment to promote its survival. The objective of this study was to characterize the effects of Campylobacter challenge on the mRNA abundance of nutrient transporters and host defense peptides (HDP), such as the avian beta-defensins (AvBD) and liver expressed antimicrobial peptide 2 (LEAP2). On the day of hatch, broiler chicks were challenged with one of three (10(6), 10(7), 10(8) colony-forming units, cfu) levels of Campylobacter jejuni. Quantitative PCR analysis revealed that there were dose-, tissue-, and agespecific changes in gene expression for both nutrient transporters and HDP. Expression of zinc transporter 1 (ZnT1) mRNA increased on d 7 in the duodenum, ileum, and cecum of birds challenged with 10(6) cfu of C. jejuni. At d 14, there was upregulation of the amino acid transporter b(o,+)AT mRNA in the duodenum, jejunum, and ileum of birds challenged with 10(6) cfu of C. jejuni. Other transporters such as EAAT3, GLUT2, SGLT1, and ZnT1 showed upregulation of mRNA in the ileum of the 10(6) cfu challenged group. There was a delayed response of the HDP to the C. jejuni challenge, with only a few HDP changed at d 7 but all HDP changed at d 14. At d 7, there was upregulation of AvBD10 mRNA in the duodenum of the 10(6) cfu challenged group but downregulation of AvBD10 in the ileum and AvBD12 and LEAP2 in the cecum of the 10(8) cfu challenged group. At d 14, there was upregulation of AvBD1, AvBD6, AvBD8, AvBD10, AvBD11, AvBD12, and AvBD13 mRNA in the ileum and cecum of the 10(6 )cfu challenged group but not the 10(7) and 10(8) cfu challenged groups compared to control. These results indicated that at a low dose (10(6) cfu) of C. jejuni, intestinal cells increased nutrient transporter and AvBD mRNA abundance to try to counter the infection, but that at higher doses the cellular response was suppressed.