ABSTRACT: Filarial infection is initiated by mosquito-derived, third-stage larvae (L3) deposited on the skin that transits through the epidermis containing Langerhans' cells (LC) and keratinocytes (KC), among other cells. This earliest interaction between L3 and the LC likely conditions the priming of the immune system to the parasite. To determine the nature of this interaction, human LC (Langerin+, E-cadherin+, CD1a+) were generated in vitro and exposed to live L3. LC exposed to live L3 for 48 h showed no alterations in cell surface markers CD14, CD86, CD83, CD207, E-cadherin, CD80, CD40, and HLA-DR or in mRNA expression of inflammation-associated genes such as IL-18, IL-18BP, and caspase 1. In contrast to L3, live tachyzoites of Toxoplasma gondii, an intracellular parasite, induced production of CXCL9, IP 10, and IL-6 in LC. Furthermore, pre-exposure of LC to L3 did not alter TLR3- or TLR4-mediated expression of pro-inflammatory cytokines IL-1β, IFN-γ, IL-6, or IL-10. Interestingly, co-cultures of KC and LC produced significantly more IL-18, IL-1α, and IL-8 than did cultures of LC alone, although exposure of the co-cultures to live L3 did not result in altered cytokine production. Microarray examination of ex vivo LC from skin blisters that were exposed to live L3 also showed few significant changes in gene expression compared with unexposed blisters, further underscoring the relatively muted response of LC to L3. Our data suggest that failure by LC to initiate an inflammatory response to the invasive stage of filarial parasites may be a strategy for immune evasion by the filarial parasite. Skin blisters from 6 healthy volunteers are either cultured in culture media alone as control samples or being exposed to 5 L3s in a transwell in a 24 well tissue culture plates for 48 hours . 12 samples were analyzed in total