Antigen Concentration in Tissues of Rabbits with Systemic Chronic Serum Sickness

The paired radiolabel technique was used to quantitate the amount of bovine serum albumin (BSA) deposited in the form of immune complexes in renal, pulmonary, splenic, hepatic, and cardiac tissues in rabbits with experimentally induced systemic chronic serum sickness (CSS). 24 h after injection, the concentrations of 125I-BSA found in the lungs, the spleen, and the kidneys of rabbits with systemic CSS induced by high doses of BSA (HDCSS) were in the same range (12.21, 10.93, and 12.68% × 10––3 injected dose/g tissue, respectively). Immunofluorescence studies demonstrated granular deposits of BSA, rabbit IgG, and C3 in the basement membranes of these organs. In rabbits during the phase between early and late proteinuric phases of CSS, 125I-BSA was present in the lung (16.85% × 10––3 ID/g tissue) and, in smaller amounts, in the kidneys, the spleen, and the liver. By immunofluorescence, immune reactants were found in phagocytic cells only. In rabbits with CSS induced by low doses of BSA (LDCSS), considerable amounts of antigen (22.72% × 10––3 ID/g tissue) were found in the kidney in late proteinuric phase, but not in other organs. In rabbits with early proteinuric phase of CSS, BSA was deposited in the kidneys (5.60% × 10––3 ID/g tissue) and, albeit in smaller amounts, in the lungs and the spleen (3.25 and 2.15% × 10––3 ID/g tissue, respectively). By immunofluorescence, scattered minimal deposits of BSA were seen in glomeruli and in pulmonary and splenic phagocytic cells. In both early and late proteinuric phases of CSS the heart did not appear to contain significant amounts of BSA. These quantitative data confirm that in rabbits with early or late proteinuric phases of CSS, BSA is deposited in the kidney and further show that comparable amounts of BSA are present in the lung and in the spleen of rabbits in the late proteinuric phase of HDCSS.