Anti-chemokine Ab’s produced by DNA vaccination block DTH response and provide subsequent protection from severe AA. (a) Eight groups of six rats each were immunized with CFA to develop poly-arthritis. Seven, 10, and 12 days after the active induction of disease, these rats were challenged (intravenously) with 200 μg of IgG (protein G purification, CNBr purification) from the different groups described in Figure 3. Control rats were injected with either PBS, IgG from naive rats, IgG from AA or from AA rats previously administered pcDNA3 alone. AA was scored daily by an observer blind to the experimental procedure. Results are shown as mean clinical score of six rats in each group ± SE. Five to 7 days after the last administration of neutralizing Ab’s to each of the above chemokines, disease severity regained the level of control AA rats (not shown). (b) Inhibition of adoptively induced DTH by anti–C-C chemokine Ab’s. Lewis rats were intravenously administered 10⁷ activated CD4⁺ PPD-specific T cells and were randomly separated into eight groups of five rats each. One hour later each group was subjected to an in vivo administration (intravenously) of various Ab’s, as described above (a). Each rat was then immunized intradermally into the dorsal surface of the ear with 10 μg PPD in 25 μL of PBS (or with PBS alone). Results are presented as mean of delta ear thickness of five different ears ± SE.