Augmentation of in vitro humoral immune responses in the mouse by an antibody to IgD.

Abstract

Heterologous anti-delta-chain antibodies have an adjuvant effect on specific in vivo humoral immune responses to simultaneously, or subsequently, injected antigens in the rat and rhesus monkey. We have used a hybridoma-secreted antibody that binds murine delta-chain of the allotype (4.22aM delta a) to study this phenomenon in the mouse and to investigate the mechanism of this effect. Injection of 4.22aM delta a into BALB/c mice removes almost all surface IgD (sIgD) from splenic B lymphocites. sIgD does not reappear until the serum level of 4.22aM delta a decreased 5-7 d after injection. 4.22aM delta a fails to induce detectable proliferation or to raise total serum Ig levels substantially above control values. However, 4.22aM dalta a injected 24 h before antigen elicits an approximately twofold enhancement of serum IgM and a 3- to 10-fold enhancement of serum IgG anti-trintriphenyl (TNP) antibodies in response to immunization with optimal doses of TNP-Ficoll or TNP-sheep red blood cells (TNP-SRBC). 4.22aM delta a injected 1 wk before or 3 d after TNP-SRBC, however, has no effect on IgG anti-TNP levels. The adjuvant effect of anti-delta-chain antibody was markedly decreased when suboptimal antigen doses were used. Furthermore, even in the case of TNP-Ficoll, a relatively T-independent antigen, the ability of 4.22aM dalta a to enhance the anti-TNP antibody response was T cell dependent. Our data suggest that the binding of anti-delta-chain antibody to cell sIgD may partially activate B lymphocytes and make them more capable of differentiating into antibody-secreting cells when stimulated by antigen-specific T cell help.

Development and pharmacological validation of novel methods of B cell activation in rat whole blood

“…Partial occupancy is not sufficient to reach the threshold for full B cell activation and therefore, we observed suboptimal B cell activation in whole blood despite stimulating with high concentrations of antiIgD (Finkelman et al, 1980;Plebani et al, 1983;Rousseaux & Bazin, 1979;Van Vollenhoven et al, 1989). Compared with dextran-coupled anti-IgD, dextran alone did not have effects on B cell activation, suggesting that the carrier molecule was not contributing to the stimulus.…”

“…However, methods of quantification of B cell activity, requiring both stimulation and detection of cellular activation in rat whole blood remain to be established. Historically, it has been a challenge to stimulate B cells in rat whole blood using soluble anti-IgM or anti-IgD to evoke BCR ligation likely as a result of the reported higher levels of endogenous immunoglobulins in rat serum compared to human or mouse serum resulting in leaching of the exogenous anti-BCR antibodies (Finkelman et al, 1980;Plebani et al, 1983;Rousseaux & Bazin, 1979;Van Vollenhoven et al, 1989). As rat is a highly relevant preclinical efficacy and safety species in drug discovery, we sought to overcome these issues and develop two different methods of B cell stimulation, using dextrancoupled anti-IgD or combined use of anti-IgD and a TLR9 agonist, in rat whole blood.…”

“…However development of BCR-mediated B cell activation assays in rat whole blood has been problematic. The exact reason for this is unclear, however the reported higher levels of endogenous immunoglobulins in rat serum compared to human or mouse serum, resulting in leaching of the exogenous anti-BCR antibodies, is likely a key contributing factor (Finkelman et al, 1980;Plebani et al, 1983;Rousseaux & Bazin, 1979;Van Vollenhoven et al, 1989). As rat is a commonly used preclinical species to evaluate drug efficacy and safety, we sought to overcome these issues and develop a BCR-mediated B cell stimulation assay in rat whole blood.…”

Physiology of IgD. I. Compensatory phenomena in B lymphocyte activation in mice treated with anti-IgD antibodies.

“…It seems reasonable to suggest that the patterns of migration and recirculation of distinctive subsets of cells (e.g., IgD-positive vs. IgD-negative cells) could account for these differences. One must also take into account the possible influence of antigen concentration and/or epitope density in antibody responses involving IgD (12,33) .…”

“…In view of the lack of suppression of the splenic PFC response to TNP-BA by mice chronically suppressed with anti-IgD, the effect of anti-IgD treatment on the in vivo response to a T dependent antigen (TNP-KLH) was determined (Table IX) . Despite the usual depression of IgD-bearing cells, there was no significant inhibition of either 7S anti-TNP PFC/spleen (geometric mean T SE) Secondary 478,630 X 1 .3 (5) 891,251 x 1 .5 (12) Percentage of IgD-bearing cells/spleen ± SE11 0 t 0 (5) 18 .4 ± 3 .4 (4) Percentage of Ig-bearing cells/spleen t SE11 6.6 ± 0 .6 ( 5 the 19S or 7S responses to TNP-KLH in homozygous mice. If any effect occurred, it was in the direction of enhancement, especially in the 19S response.…”