Enhancement of mouse contact hypersensitivity appears with a short chain triacylglycerol but not with a long chain one.

The prevalence of skin allergies could be partly due to the increased exposure to chemicals from consumer products. Chemicals that can enhance hypersensitivity caused by other chemicals are the focus of this study. We have demonstrated that phthalate esters with short chain alcohols enhance fluorescein isothiocyanate (FITC)-induced contact hypersensitivity (CHS) in a mouse model. We have also found that tributyrin, a triacylglycerol (TAG) with three butyric acids, enhances sensitization to FITC. To elucidate such an enhanced skin sensitization might be based on a general feature of TAG, we compared tributyrin and triolein, a natural TAG, as to an adjuvant effect on FITC-CHS. Triolein is the dominant TAG in olive oil and contains long chain mono-unsaturated fatty acids. Unlike tributyrin and dibutyl phthalate (DBP), triolein did not exhibit an adjuvant effect. With triolein, enhancement of FITC-presenting CD11c⁺ dendritic cell trafficking to draining lymph nodes was weak, and the activation status of DC, as revealed as CD86 expression, was low. We found a difference in the pattern of skin cytokine production, i.e., that thymic stromal lymphopoietin was produced with DBP and interleukin-1β with tributyrin. Triolein did not induce either of these cytokines. This illustrates that the adjuvant effect of tributyrin on FITC-CHS is not a general phenomenon for TAGs. Although beneficial effects may be expected through oral administration of tributyrin, the effect on skin immune systems should be considered.