Studies of the acute phase response in experimental serum sickness

The acute phase behavior of C-reactive protein (C-RP), the third component of complement (C3) and total haemolytic complement activity was studied during the course of acute serum sickness (ASS) in rabbits. The specific aim was to establish whether the induction protocol caused a significant change in the serum concentration of proteins (such as C3) which could modify the outcome of the disease. ASS was induced by an intravenous (IV) bolus of bovine serum albumin (250 mg/Kg) with or without prior subcutaneous (SC) immunization with 4 mg BSA in complete Freund's adjuvant. Thirty-six animals received a full induction regimen (i.e., both SC and IV BSA). A further six rabbits were given either IV or SC BSA alone, in order to define the basis for acute phase changes observed when both injections were given. Twelve animals received a standard acute phase stimulus with intramuscular (IM) turpentine--2 or 3 ml--as a comparison to the response observed in the experimental animals. Nine, 14 and 24 animals showed a rise in C-RP (i.e., five-fold increase), C3 and haemolytic activity (greater than 25% increase) respectively after a full induction protocol. Eight, nine and five animals showed a comparable rise with IM turpentine. Studies with IV or SC BSA alone showed that the latter was predominantly responsible for the rise in C-RP and haemolytic activity. Specifically, five and four animals respectively showed a significant rise in these two parameters. Three animals showed a rise in C-RP following IV BSA alone.(ABSTRACT TRUNCATED AT 250 WORDS)