25hydroxy vitamin d3 modulates dendritic cell phenotype and function in crohns disease background in crohns disease crd vitamin d may help to balance an exaggerated immune response and thereby improve the disease course the immunomodulating effects depend on the activation of 25hydroxy vitamin d3 25d3 into 125dihydroxy vitamin d3 125d3 this activation has previously been shown to take place in dendritic cells dc from healthy individuals we hypothesised that dc from crd patients are able to regulate and control inflammatory responses through 25d3 activationmethods during differentiation monocytederived dc from 20 crd patients were cultured with either 25d3 or 125d3 and matured with lipopolysaccharide lps we examined dc surface marker expression cytokine production and the ability to induce cell proliferation in an allogeneic mixed leukocyte reactionresults following stimulation with lps dc exposed to either 25d3 or 125d3 exhibited lower expression levels of cd80 cd83 cd86 and hladr and diminished tnf production compared with dc cultured with lps alone in contrast cd14 expression and il6 production were higher following 25d3 or 125d3 treatment compared with lps alone both forms of vitamin d3 reduced the ability of dc to activate lymphocytesconclusions following stimulation with 25d3 dc from crd patients displayed a reduced response to lps with a diminished capability to activate t cells compared with dc stimulated with lps alone these data indicate that intrinsic activation of 25d3 occurs in dc from crd patients and show that 25d3 can modulate dc function in crd our data suggest that vitamin d deficiency may contribute to the uncontrolled inflammatory process seen in crd