The macrophage-phagocyte system in rabbits with experimentally induced serum sickness: functional studies

The objective of this study was to measure the phagocytic functions of the spleen and the liver and, if possible, to correlate them with the morphology and the immunohistology of these organs in rabbits with serum sickness. Serum sickness was induced by repeated intravenous injections of bovine serum albumin (BSA). Rabbits with acute serum sickness (stage A of serum sickness), with chronic serum sickness (stage C), rabbits in a stage of immunization between stage A and stage C (stage B), and rabbits that did not respond to the antigenic challenge [nonresponders (NR)], as well as nonimmunized (NI) rabbits were used. The function of the spleen and of the liver was measured by the clearances of 51Cr-labeled heat damaged (HE), periodate-treated (PE), or immunoglobulin G (IgG)-coated (IgGE) autologous erythrocytes. In NR rabbits the functions of the spleen and liver were normal. In rabbits in stage A of serum sickness the clearance of HE, the only one measured in this stage, was decreased. In rabbits in stage B the clearances of HE and IgGE were determined; both clearances were decreased. In rabbits in stage C, the clearances of HE and IgGE were decreased, while the time of clearance of 50% (T 1/2) of PE was not significantly prolonged. In addition, in rabbits in stages A, B, and C the ratio of whole spleen vs liver radioactivity was increased. In rabbits in stage B the clearance of HE returned to normal 3 days after discontinuation of BSA injections. While all animals with detectable morphologic and immunohistologic changes of the spleen and the liver had prolonged clearances of treated erythrocytes, some animals with similarly prolonged clearances lacked evidence of pathology of these organs. The results obtained indicate that: (1) In NI and in NR rabbits, treated erythrocytes are rapidly removed by the macrophage-phagocyte system (MPS) and preferentially by the liver. (2) In rabbits in stages A, B, and C of serum sickness the clearances of treated erythrocytes are significantly prolonged. Moreover, treated erythrocytes appear to be preferentially removed by the spleen, indicating that the ability of the spleen to clear treated erythrocytes is less impaired than that of the liver. (3) In stages A, B, and C of serum sickness the nonimmunologic clearance of autologous erythrocytes is as altered as the clearance that occurs via Fc receptors. (4) In rabbits in stage B of serum sickness recovery of MPS function occurs after the interruption of BSA injections, suggesting reversible damage.(ABSTRACT TRUNCATED AT 400 WORDS)