In article <Ct798C.CDq at news.cis.umn.edu>, shiv at hiv.med.umn.edu (Shiv A.
Prasad (MicroBio)) writes:
>"OK, so dogma (i.e last review I read on DC's) states that dendritic
cells are not phagocytic and do not express FcR's. How then would these
cells present Ag? Are peptides merely loaded onto empty class II
molecules,
do they displace class II with weakly-bound peptides, or is pinocytosis
responsible for Ag uptake?"
> DC are phagocytic (see J. Exp. Med. (1993) 178:509 and J. Exp. Med.
(1993) 178:479) and can take up soluble ag via Fc receptors, even better
than B cells can via surface Ig (see J. Exp. Med. (1994) 179:1109). The
important feature to bear in mind is that antigen uptake and processing
are properties of immature DC which have Fc and possibly other receptors
(e.g. mannose receptors) which can participate in antigen acquisition.
There is also unpublished evidence that immature DC may be able to
macropinocytose constitutively, thereby sampling large amounts of
fluid-phase antigens from the extracellular milieu.
See references in those articles for reviews on immature vs. mature DC.
Caetano Reis e Sousa, NIH, Bldg. 10, Rm. 11D15, Bethesda MD 20892
