DEC-205lo Langerinlo neonatal Langerhans' cells preferentially utilize a XXXX -sensitive, fluid-phase pathway to internalize exogenous antigen.

@entity52471 @entity19 @entity2822 @entity1600 @entity2307 @entity3913 @entity2823
Antigen treatment of neonatal epidermis results in antigen-specific immune suppression. Compared with adult counterparts, neonatal Langerhans' cells (LC) demonstrate an impaired ability to transport antigen to the @entity1600 ( @entity1600 ). As it is possible that neonatal LC have a reduced ability to endocytose antigen, we evaluated the acquisition of endocytic function, the expression of uptake receptors and the internalization of soluble and small particulate antigens in neonatal, juvenile and adult @entity19 . Although LC from 4-day-old @entity19 were weakly positive for the @entity3913 -type receptor, @entity52471 , they were capable of internalizing @entity2822 ( @entity2823 )-dextran, but to a lesser extent than LC from 6-week-old @entity19 . However, when ratio data were calculated to account for variations in fluorescence intensity at 4 degrees, it was demonstrated that neonatal LC continued to internalize antigen over a longer period of time than adult @entity19 and, as the ratios were much higher, that neonatal cells were also relatively more efficient in antigen uptake. When receptors for mannan and @entity3913 were competitively blocked, LC from neonatal @entity19 , but not adult @entity19 , could still efficiently internalize @entity2823 -dextran. Consequently, the uptake of @entity2823 -dextran, in part, occurred via alternative receptors or a receptor-independent fluid-phase pathway. A feasible pathway is macropinocytosis, as LC from 4-day-old @entity19 demonstrated a reduction in @entity2823 -dextran internalization by the macropinocytosis inhibitor, @entity2307 . Evidence of a functional macropinocytosis pathway in neonatal LC was further supported by internalization of the soluble tracer Lucifer Yellow (LY). We conclude that neonatal LC preferentially utilize a @entity2307 -sensitive, fluid-phase pathway, rather than receptor-mediated endocytosis, to internalize antigen. As neonatal LC are capable of sampling their environment without inducing immunity, this may serve to avoid inappropriate immune responses during the neonatal period.
