Anergic T cells metabolize chemokines via CD26. CXCL12 was added to chemotaxis medium (RPMI 2% FCS) at a concentration of 50 ng/mL and incubated overnight at 37°C 7% CO2 in the absence of T cells (panel A) or in the presence of responsive (panel B) or anergic human CD4⁺ T cells (panel C). As a control, chemotaxis medium (RPMI 2% FCS) alone, or containing either responsive (10⁶/mL) or anergic (10⁶/mL) human T cells, was used. The results are expressed as percentage of migrated naive T cells after 6 hours and are reported as the average of at least 3 experiments of identical design. The bars show the SD. * indicates statistically significant (P < .005) versus control cultures (CXCL12 incubated with anergic T cells). (Panels D-E) In some experiments responsive (R) and anergic (A) T cells (10⁶/sample) were treated with an antihuman CD26 antibody (5 μg/mL) for 30 minutes and washed prior to incubation with CXCL12 as described in “Anergic T cells metabolize chemokines via CD26.” Supernatant was then obtained from each sample (as specified below each column) by centrifugation and the chemotactic activity was assessed monitoring the migration of purified CD45RA⁺ T cells (2 × 10⁶/well) through a transwell after 6 (panel D) and 24 (panel E) hours. The results are expressed as specified for panels A-C. * indicates statistically significant (P < .006, panel D; P < .001, panel E) versus control cultures (CXCL12 incubated with anergic T cells).