The Effect of Passively Administered Antibody on Antibody Synthesis

Abstract

Suppression of the primary response of rabbits to intravenously administered KLH can be achieved with very small amounts of hyperimmune anti-KLH administered a day later since the rabbit apparently rapidly eliminates most of the KLH by nonimmunologic means. The amount of passive anti-KLH needed to achieve immunosuppression was directly proportional to the dose of injected antigen. Antibody passively administered as much as 6–8 days after antigen still can be strongly immunosuppressive, which suggests that the antibody must be reacting with immunogen in or on responding cells or perhaps in the process of transfer between cells. There was no evidence that the presence of passively administered hyperimmune anti-KLH prior to the injection of antigen had any immunosuppressive action beyond the direct neutralization of the injected antigen. When KLH was injected in Freund adjuvant, anti-KLH incorporated with the KLH in the adjuvant was much more efficient in causing immunosuppression than anti-KLH given intravenously. The primary responses to 2 mg KLH given intravenously and 2 µg given in adjuvant reached approximately equal peaks and were suppressible by comparable amounts of intravenously administered anti-KLH. Two observations suggest that passive antibody neutralizes the immunogenic stimulus at the level of individual antigenic determinants and not merely by aggregating or precipitating entire antigenic molecules. First, anti-abalone hemocyanin (AH) which cross-reacts approximately 50% with KLH was only partially immunosuppressive even in extremely large amounts, i.e., amounts which could react with and precipitate much more KLH than could the smaller but more suppressive doses of anti-KLH. Second, when KLH and anti-KLH were given together in adjuvant, effective immunosuppression was achieved only with amounts of anti-KLH sufficient to saturate or cover virtually all available antigenic determinants. The immunosuppressive quality of passive antibody increases with time after immunization and with repeated immunization of the donor. In view of their relatively weak immunosuppressive properties, antibodies formed in the first weeks of a primary response may not contribute significantly to the turning off of the antibody response. In any event, results obtained by passive transfer of hyperimmune antibody to animals early in a primary response cannot be applied to the natural events in a primary response.

The X-Y-Z Scheme of Immunocyte Maturation

“…The inhibitory effect of specific antibody on further antibody production has been well documented in sheep red cell systems (31)(32)(33), antiphage systems (34), and protein antigen systems (35). However it seemed doubtful that antibody feedback was responsible for the refractoriness of these exhausted nodes for two reasons.…”

Regulation of the Immune Response

“…In the present studies, antibody preparations were incubated for i hr at 37°C in vitro to insure that most of the antigenic determinants had combined with antibody, but the amount of antibody at high concentrations was well in excess of the amount which could actually be absorbed by the low concentration of erythrocytes (unpublished observations), so that rapid excretion could be a factor in the lack of suppressive activity of F(ab')2 antibody. The intact 7S antibody may localize in such a way that it contacts antigen which is most relevant to the immune response (that is, antigen which is in a position to initiate an immune response), whereas F(ab')2 antibody does not localize in imrnunologically relevant sites and inter-acts with any antigen, whether or not the antigen is in a position to initiate the immune response (29). Low doses of F(ab')~ antibody preparations show signs of enhancing priming, and this may indicate that complete exclusion from the immune response mechanism (by elimination or localization) cannot be the whole explanation since this should lead to no change whatsoever.…”

An Approach to the Quantitation of Immunogenic Antigen

“…Earlier, it was determined that anti-KLH mixed with the KLH and incorporated in incomplete Freund's adjuvant could suppress the expected antibody response. In this situation, 12/zg anti-KLH mixed with 2/zg KLH inhibited the antibody response approximately 80 % over the first month (2). Making the conservative estimate that all KLH in the adjuvant mixture was immunogenic, the anfi-KLH/KLH weight ratio needed for effective suppression was at least six.…”

“…The results are expressed as micrograms of dissociated KLH nitrogen precipitated by 1 ml of antiserum at the point where 800/0 of the KLH added is precipitated (pS0). 1 anti-KLH ps0 unit consists of about 11/zg antibody protein (2).…”

“…The experimental design was based on the results of numerous studies of the inhibition of antibody synthesis by passively administered antibody. It appears clear that this inhibition is caused by the neutralization of the antigenic stimulus by the passive antibody (reviewed by Uhr and Mtiller) (1) and, further, that the effective block is at the level of individual antigenic determinants (2,3). If, as seems likely, this inhibition involves combination of passively administered antibody with immunogenic antigenic determinants, then the antibody so combined should be able to be differentiated from free uncombined antibody and the amount of this combined antibody should be proportional to the amount of immunogenic antigen, plus any residual nonimmunogenic antigen available to react with the antibody.…”