Concentration of CCL8 in human sera. Concentration of CCL8 in human sera was determined by ELISA for human CCL8. All sera from those who did not develop GVHD after HSCT (non-GVHD/HSCT) contained less than 48 pg/mL (mean ± SE: 22.5 ± 5.5 pg/mL, range: 12.6-48.0 pg/mL, n = 7). CCL8 was highly up-regulated in GVHD plasma (GVHD/HSCT) ranging from 52.0 to 333.6 pg/mL (mean ± SE: 165.0 ± 39.8 pg/mL, n = 7). Two patients with severe, eventually fatal, GVHD showed extremely high levels of CCL8 (ie, 333.6 and 290.4 pg/mL). In healthy controls (donors), mean concentration of CCL8 was 18.9 pg/mL (range: 0.00 to 32.6 pg/mL, n = 8). The difference in serum concentration of CCL8 was statistically significant between non-GVHD and GVHD plasma obtained from patients undergoing HSCT.