T-cell proliferation responses. (a) From the six animals in Experiment III, a longitudinal analysis of collagen type II (CII)-specific T-cell responses in freshly isolated peripheral blood mononuclear cells (PBMC) shows a variable response against denatured CII (animal identification at top of the graph). #Day of necropsy. (b) At the day of necropsy, CII-specific proliferative responses were measured from the six animals in Experiment III. Cells isolated from the lymph nodes (spleen, axillar and inguinal) show better responses than cell isolated from the PBMC. (c) From 10 animals in Experiment II, the CII-specific responses were analyzed using dilution of the vital dye carboxyfluorescein succinimidyl ester in combination with cellular staining for the T-cell markers CD3, CD4 and CD8. It was shown for four out of the 10 animals analyzed that, especially in axillar and inguinal lymph nodes (LN), both CD3+/CD4+ T cells and CD3+/CD8+ T cells contribute to the CII-specific cellular responses (a representative experiment of those four animals is presented; animal M04111). Stimulation index = proliferation of experimental sample (counts per minute)/proliferation of medium control (counts per minute). ch-CII, chicken-origin collagen type II; PID, post induction day.