Background: Cathelicidins are a family of Host Defense Peptides (HDPs), that play an
important role in the innate immune response. They exert both broad-spectrum antimicrobial
activity against pathogens, and strong immunomodulatory functions that affect the response of
innate and adaptive immune cells.
Objective: The aim of this study was to investigate immunomodulation by the chicken cathelicidin
CATH-2 and compare its activities to those of the human cathelicidin LL-37.
Methods: Chicken macrophages and chicken monocytes were incubated with cathelicidins.
Activation of immune cells was determined by measuring surface markers Mannose Receptor Ctype
1 (MRC1) and MHC-II. Cytokine production was measured by qPCR and nitric oxide
production was determined using the Griess assay. Finally, the effect of cathelicidins on
phagocytosis was measured using carboxylate-modified polystyrene latex beads.
Results: CATH-2 and its all-D enantiomer D-CATH-2 increased MRC1 and MHC-II expression,
markers for antigen presentation, on primary chicken monocytes, whereas LL-37 did not. D-CATH-
2 also increased the MRC1 and MHC-II expression if a chicken macrophage cell line (HD11 cells)
was used. In addition, LPS-induced NO production by HD11 cells was inhibited by CATH-2 and
Conclusion: These results are a clear indication that CATH-2 (and D-CATH-2) affect the
activation state of monocytes and macrophages, which leads to optimization of the innate immune
response and enhancement of the adaptive immune response.