Low affinity antibody production in mice - a form of immunological tolerance?

Dietary antigen handling by mother and offspring

Sows were fed ovalbumin (OvA) as a novel protein antigen either throughout gestation and lactation (G + L) or during lactation only (L). This resulted in a significant uptake of OvA into blood, colostrum and milk along with a specific IgG response. In piglets from the G + L group, OvA and antibodies to OvA were detected in serum after ingestion of colostrum. In a large proportion of these piglets OvA was still detected at 3 weeks of age. In the L group a significant proportion of the piglets responded to OvA whilst still suckling their mother. At 3 weeks of age all piglets were weaned onto an egg-based diet. A similar uptake of OvA was seen in all piglets but there was no response to OvA in the G + L piglets. In piglets from sows fed only during lactation, however, a rapid IgG anti-OvA response and signs of diarrhoea were seen. The results suggest that factors of immunological importance are passed over from mother to offspring and it is proposed that immunological experience of dietary antigens by the mother is important for a 'safe' tolerance induction in her offspring.

Measurement of relative avidity of antibodies reactive with Porphyromonas (Bacteroides) gingivalis in the sera of subjects having adult periodontitis

Relative avidities of antibodies to Porphyromonas (Bacteroides) gingivalis in the sera of 15 patients having adult periodontitis and 15 healthy subjects were evaluated using an ammonium thiocyanate-dissociated ELISA. Graded concentrations of ammonium thiocyanate were added to a single dilution of serum in order to dissociate low avidity antibody binding to P. gingivalis. The concentration of thiocyanate resulting in 50% reduction in binding (absorbance) was termed the ID50 for that serum. When IgG-class antibodies were examined, the ID50 of anti-P. gingivalis antibodies in the sera of patients was significantly elevated (0.96M vs 0.71M; p less than 0.01, Student's t-test). In contrast, when IgM-class antibodies were examined no significant differences in ID50 between patients and controls were found for P. gingivalis (0.54M vs 0.53M). While the ID50 values of patient antibodies were found to be elevated relative to those of healthy controls, comparison with antibodies from rabbits immunized with P. gingivalis and with ID50 values from other human studies suggests that adult humans, in general, produce very low-avidity antibodies to P. gingivalis. It is suggested that the presence of low-avidity antibodies contributes to the pathology associated with periodontal disease.

Prostaglandin E2 production is enhanced in mice genetically selected to produce high affinity antibody responses

Spleen cells from mice selectively bred to produce high affinity antibody responses to protein antigens (HI) had reduced responses to both T and B cell mitogens when compared to those from mice selectively bred to produce low affinity (LO) responses. The reduced response by spleen cells from HI mice was partially reversed by the addition of indomethacin in vitro. Spleen adherent cells from HI mice had increased production of prostaglandin E2 when compared to those from LO mice. In addition, spleen adherent cells from mice which fail to show affinity maturation not only produced lower amounts of PGE2 than those from HI mice but also a decreased proportion of spleen cells adhered to plastic in these mice. To test the possibility that the increased PGE2 production in HI mice was responsible for the production of high affinity antibodies, indomethacin was administered in vivo and resulted in a significant reduction in antibody affinity. The possibility that PGE2 production may control the balance between the TH1 and TH2 cells of Mosmann and Coffman is discussed.

Immunoquantitation of antibody to placental phosphatase by single radial immunodiffusion; effect of antibody avidity and immunization protocol

The radial immunodiffusion method was used to titer antisera to human placental alkaline phosphatase. When this was done with diluted enzyme and antisera, it was found that early-course antisera consistently yielded low titers. This observation was consistent with the known low avidity of such antisera.

Genetic and nutritional variations in antigen handling and disease

Low function (deficiency), within the 'normal range', of each of five immunity functions is associated with immunopathological disease, and/or defective antigen handling. These are probably genetically determined, either polygenic or single gene, but environmental factors such as diet influence them greatly, and the vulnerability may be especially great in the newborn period. The relevant systems are those involved in the immune elimination of antigen (antibody and macrophages) and those possibly involved in the immune exclusion of antigen (IgA, the alternative pathway of complement, and cilial action). The gut has an especially complicated role in antigen-handling, and feeding influences its capacity to do so. Eczema was prevented by a regimen of neonatal antigen avoidance, which was largely breast-feeding, and it is likely that other immunopathological diseases result from antigen contact during periods of malnutrition. The mechanisms of such effects are likely to be complicated, but adjustment of the environment to suit the genetically vulnerable, particularly in the newborn period, can lead to the prevention of disease.