MOUSE THYMIC DENDRITIC CELL SUBPOPULATIONS

Mouse thymic dendritic cells (DC) have been isolated after collagenase digestion, selection of the low-density cell fraction, then depletion of T-lineage cells and other non-DC by treatment with specific monocl onal antibodies (mAb) and removal with anti-Ig-coated magnetic beads. The resulting DC preparation represented 0.1-0.2% of total thymic cell s and contained 70-80% DC. Flow cytometry analysis of MHC class II (MH C II) expression by DC showed that 40% of DC expressed intermediate le vels of MHC II, and 60% expressed high levels of this marker. Moreover , immunofluorescent 2-colour staining allowed the characterization of two clearly distinguishable DC subpopulations: MHC II(inter) DC were C D45hi, CD44hi, HSA(hi), whereas MHC II(hi) DC were CD45lo, CD44lo, HSA (lo). These results are discussed with regard to the functional signif icance of MHC II(inter) and MHC II(hi) DC subpopulations in the mouse thymus.