International Immunology, Vol. 14, No. 3, 309-318,
March 2002
© 2002 Japanese Society for Immunology
Overexpression of rab7 enhances the kinetics of antigen processing and presentation with MHC class II molecules in B cells
Departments of Immunology and
1 Medical Biophysics, University of Toronto, Medical Sciences Building,1 King's College Circle, Toronto, Ontario M5S 1A8, Canada
Correspondence to: T. H. Watts; E-mail: tania.watts{at}utoronto.ca
rab7 is an intracellular GTPase involved in early to late endosome fusion. By overexpressing rab7 in a B lymphoma we show that the rate of antigen presentation with MHC class II molecules is increased for four different peptide–MHC combinations, under conditions where levels of other components of the antigen-processing pathway remained constant. Resting B cells were shown to express significantly lower levels of rab7 when compared to adherent macrophages or to `immature' or `mature' dendritic cells. rab7 expression was up-regulated by stimulation of B cells with lipopolysaccharide or CD40 ligand. Other components of the endocytic pathway were also up-regulated in activated B cells, suggesting that B cell activation leads to a general enlargement of the endocytic compartment, correlating with the increased ability of activated B cells to process antigen. Taken together, our results suggest that rab7 levels regulate the rate of antigen presentation in B cells, and that rab7 and late endocytic compartments are important in MHC class II-restricted antigen presentation in B cells.
Keywords: CD40 ligand, dendritic cells, endocytic pathway, GTPase
1 Present address: Hematopoiesis Department, Holland Laboratory, American Red Cross, Rockville, MD 20855, USA