Examination of interleukin-1 activity, the acute phase response, and leukocyte subpopulations in rats with adjuvant-induced arthritis.

Rats with adjuvant-induced arthritis (AA) were used to determine whether chronic systemic paw inflammation was accompanied by appearance of the acute phase response, an increase in splenic interleukin-1 (IL-1) production, and a reduction of nonhelper T cells in the spleen and peripheral blood. Two weeks after injection of adjuvant, the rats developed significant (P less than or equal to 0.01) swelling of the noninjected paw indicative of systemic inflammation. The rats with AA also exhibited signs of the acute phase response, as measured by a significant increase in plasma C-reactive protein (138% above normal) and a significant decrease in plasma albumin (47% below normal), zinc (30% below normal), and iron (58% below normal). IL-1 production from spleen cells of rats with AA was increased 115% compared with normals. Results from immunofluorescence studies with W3/25 and OX8 antibodies to distinguish rat T-helper-inducer (TH) spleen cells from suppressor-cytotoxic (nonhelper T) spleen cells indicated no significant difference between the percentage of OX8+ cells in spleens of arthritic rats compared with OX8+ cells in spleens of normal rats. The W3/25+-to-OX8+ ratio of 1.6 +/- 0.2 for normal rat spleen cells (33% to 21%) was not significantly different from the arthritic rat ratio of 1.9 +/- 0.1 (36% to 19%). When the phenotypes of peripheral blood mononuclear cells were analyzed, the normal animals possessed a greater percentage of W3/25+(TH) cells than did rats with AA. Normal blood mononuclear cell samples were composed of 51% +/- 3% W3/25+ cells and 22% +/- 2% OX8+ cells, and the samples from rats with AA contained 43% +/- 4% W3/25+ cells and 24% +/- 3% OX8+ cells. Thus, the helper-to-nonhelper ratio was higher for normal rats (2.3 +/- 0.1) than for arthritic rats (1.8 +/- 0.2). The data indicated that the appearance of the acute phase response and the abnormally high rate of splenic IL-1 production in the rats with AA did not stem from a subnormal percentage of OX8+ nonhelper T cells in the spleen or peripheral blood.