DCs loaded with matched class I and II antigens exhibit enhanced IL-12 secretion and CD83 expression. (A) Double-loading of DCs with matched MHC class I and II determinants enhances DC IL-12 secretion in a single-antigen system. equals IL-12 secretion from DCs loaded with matched class I (plasmid) and class II (soluble protein). □ equals IL-12 secretion from other DC loaded by any other method. y-axis: pg IL-12/mL/10⁶ cells (A,B,D). (B) Double-loading of DCs with matched MHC class I and II antigens enhances DC IL-12 secretion. Eight experiments shown (double unmatched, 5 experiments shown). (C) Double-loading of DC with matched class I and II determinants causes enhanced up-regulation of CD83 expression. Average MFI value of unloaded and singly loaded DCs equals 0. □ equals percent by which CD83 MFI of all unloaded or singly loaded DCs differs from the average. equals percent by which CD83 MFI of all doubly loaded DCs differs from the average (P < .001). y-axis equals percent difference of CD83 MFI of CD83⁺ DC from the average of unloaded and singly loaded DCs. (D) Loading of DC MHC class I by electroporation of rHA and class II by incubation of rHA¹¹  enhances DC IL-12 secretion. equals IL-12 secretion from DCs loaded with matched class I and class II proteins (rHA). □ equals IL-12 secretion from DC loaded singly or loaded doubly with disparate class I and class II antigens (ie, rHA and luciferase).