The responses to stimulation with TLR ligands further revealed the difference between the two groups of differentiated BMDC. The BMDC exposed to rHp-CPI during its differentiation showed significantly lower percentages

of CD40+, CD86+ and MHC-II+ check details cells and IL-6, IL-12p40 and TNF-α cytokine production when stimulated with TLR9 ligand CpG compared with the BMDC that were not exposed to rHp-CPI. Interestingly, the two groups of BMDC generated with or without exposure to rHp-CPI respond in similar manners to stimulation with TLR4 ligand LPS. It is known that a number of cysteine proteases are involved in signalling pathways associated with some TLRs. Proteolytic cleavage of TLR9 by cathepsins is required for TLR9 signalling. The BMDC from cathepsin L-deficient and S-deficient mice

showed impaired responses to stimulation with CpG, but the response to LPS stimulation remained unchanged Trichostatin A price compared with the BMDC from normal wild-type mice.[37] Our results that BMDC generated in the presence of rHp-CPI exhibit impaired responses to CpG stimulation, but showed unchanged responses to LPS stimulation, are consistent with the observations made on BMDC from cathepsin-deficient mice. We then further analysed the modulatory effects of rHp-CPI on differentiated immature BMDC and observed that rHp-CPI treatment alone had no significant effect on DC activation, as shown by the expression of CD40, CD80 and CD86 that was comparable with those detected on control BMDC. In addition, rHp-CPI treatment alone failed to induce production of IL-16, IL-12p40 and TNF-α. These results indicate that the rHp-CPI protein of parasite origin has a negligible effect on differentiated immature

BMDC. However, it was observed that rHp-CPI modulates the responses of immature BMDC to stimulation with LPS and CpG. Treatment of immature BMDC with rHp-CPI reduced the CD40 and CD86 expression and IL-6 and TNF-α cytokine production by immature BMDC induced by stimulation with CpG. Treatment with rHp-CPI also suppressed the expression of CD80 and MHC-II molecules and IL-6 production of these BMDC induced by LPS stimulation. These results suggest that rHp-CPI modulates the TLR-associated signalling pathways differently at the different stages of BMDC development. In addition to the modulation effects on responses to stimulation with TLR-associated signalling pathways, rHp-CPI treatment also resulted in impaired antigen-presenting function of BMDC. Cysteine proteases in endosomes and lysosomes of antigen-presenting cells are known to be involved in the processing of protein antigens and MHC-II molecule maturation. Cathepsin S plays an important role in stepwise proteolytic degradation of the invariant chain (Ii) that regulates MHC-II molecule intracellular trafficking and protects the MHC-II molecule from premature binding of antigen peptide.