Fig. 4. β-Endorphin content in CD45+immune cells by radioimmunoassay. The CD45+cells were positively selected by magnetic cell separation (A ), and END content was determined by radioimmunoassay (B ). Efficacy of CD45 cell separation by magnetic beads was verified by flow cytometry (representative sample at 96 h after injection of Freund’s complete adjuvant (FCA); (upper panel , unselected;middle panel , negative selection;lower panel , positive selection [A ]). The amount of END in CD45+cells, calculated per one paw, increased substantially during the course of inflammation (mean ± SD; 2 h, n = 2; 6 and 96 h, n = 3;P < 0.05 by analysis of variance on ranks [B ]).