THE CATABOLISM OF ALLOANTIBODY IgG2a IN NORMAL AND HOMOGRAFT TOLERANT RATS

Abstract

Summary. Alloantibody was raised in PVG/c rats against DA rats. The calaholism of alioaniibody in normal PVG/c rats and PVG/c rats tolerant to DA rals was followed after intravenous injection. A haemaggluUnation assay was used to detect alloantibody activity. The half-life time of alloantibody IgG2a in the normal PVG/c rats was 10 days. On the other hand, in the PVG/c rats tolerant to DA rats, the half-life of alloantibody lgG2a varied. The rats could be divided into three groups. Group A; alloantibody IgG2a was eliminated from ihe circulation very rapidly. Group B: alloantibody lgG2a disappeared from the circulation relatively rapidly and was maintained at a low level in the plasma but then increased to a high titre. This peculiar pattern ofGroup B seems to be due to the endogenous production of alloantibody. In this case abrogation of tolerance took place. Group C: the pattern of elimination of this group was almost identical to that of normal rats.The biological significance of the plasma decay of alloantibody IgG2a in the normal and homograft tolerant rats has been considered. It is concluded from tbe present results that alloantibody might be important in some cases for tbe maintenance of homograft tolerance. INTRODUCTIONIn spite of the amount, class and the heterogeneous nature of immunoglobulin synthesised during an immune response, there appears to be very intricate regulation of immunoglobulin synthesis. This regulation could be mediated by several factors, such as the fate and presence of antigen, by cells involved in the immune response or antibody. In most cases following challenge with antigen, the level of antibody reaches a peak and decreases gradually in the circulation to fmally disappear. Some antigens such as bacterial lipopoly-

Effect of donor specific transfusion (DST) is restricted to the rat combination used and closely related with alloantibody in heart transplantation

“…In the neonatal allograft tolerant rats, alloantibody levels could not be detected by the haemagglutination assay, but in rats in which the allograft tolerance was abrogated by means of alloantibody injection, alloantibody production occurred (20). In liver transplantation of the non-rejector combination (DA to PVG) the anticlass I levels were low or could not be detected, but the anti-class II antibody levels were found to be high (21).…”