Comparison of the PCV2 re-stimulation profile for freshly isolated compared to frozen and then in vitro expanded PBMC. PBMC were re-stimulated with PCV2, mock antigen, or medium alone directly after isolation ("PBMC fresh; 24 h"). Aliquots of the PBMC were frozen under liquid nitrogen, before thawing and expanding by culture in the presence of rpoIL-2 together with PCV2, mock antigen, or medium alone. This expansion was for 24 h ("PBMC thawed; 24 h"), 3 days ("PBMC thawed; 3 days") or 5 days ("PBMC thawed; 5 days") prior to analysis for IFN-γ SC by the ELISPOT assay. Means of triplicates +/- SD of two experiments are shown.