Comparison between thymus- and spleen-derived B-cell hybridomas

On the maternal transmission of immunity: a 'molecular attention' hypothesis

Maternally-derived antibodies can provide passive protection to their offspring. More subtle phenomena associated with maternal antibodies concern their influence in shaping the immune repertoire and priming the neonatal immune response. These phenomena suggest that maternal antibodies play a role in the education of the neonatal immune system. The educational effects are thought to be mediated by idiotypic interactions among antibodies and B cells in the context of an idiotypic network. This paper proposes that maternal antibodies trigger localized idiotypic network activity that serves to amplify and translate information concerning the molecular shapes of potential antigens. The triggering molecular signals are contained in the binding regions of the antibody molecules. These antibodies form complexes and are taken up by antigen presenting cells or retained by follicular dendritic cells and thereby incorporated into more traditional cellular immune memory mechanisms. This mechanism for maternal transmission of immunity is termed the molecular attention hypothesis and is contrasted to the dynamic memory hypothesis. Experiments are proposed that may help indicate which models are more appropriate and will further our understanding of these intriguing natural phenomena. Finally, analogies are drawn to attention in neural systems.

Alteration of idiotypic connectivity in prenatally tolerized neonatal mice

Prenatal tolerization with trinitrobenzenesulphonic acid (TNBS) leads to expansion of trinitrophenyl (TNP)-specific B cells, the majority of which become refractory to stimulation during postnatal development. One possible explanation could be that they belong to the repertoire of naturally activated B cells which are limited in expansion after antigenic stimulation due to a high degree of idiotypic connectivity. To evaluate this hypothesis, 59 thymus- and 490 spleen-derived B-cell hybridomas from 6-day-old prenatally untreated and prenatally TNBS-treated mice were tested for reactivity against 33 arbitrarily chosen clones derived from the same fusions, 17 being derived from control and 16 from tolerized litters. Two major points could be deduced: (1) Idiotypic connectivity, including connectivity of TNP- and anti-TNP-reactive monoclonal antibodies (MoAb), was maintained after prenatal tolerization. This accounted for thymus- and spleen-derived MoAb. (2) Only TNP- and anti-TNP-reactive MoAb derived from prenatally untreated and prenatally tolerized mice displayed significantly distinct idiotypic profiles. Differences were pronounced, especially with thymus-derived MoAb. Thus, TNP-specific B cells in prenatally tolerized newborns do not behave like B cells of adult mice stimulated by external antigen, but rather like a part of the naturally activated, idiotypically connected B-cell repertoire of the newborn. This could explain B-cell unresponsiveness at older age as a consequence--at least partly--of their high idiotypic connectivity.

Intrathymic T cell repertoire after prenatal trinitrobenzene-sulfonic acid-treatment

It is still a matter of debate, whether tolerance toward self-non-MHC antigens is due to intrathymic deletion or to regulatory processes in the periphery. To further pursue this question, responsiveness toward TNP and an anti-TNP monoclonal antibody (Sp6) carrying a recurrent idiotype was evaluated in prenatally trinitrobenzenesulfonic acid (TNBS)-treated mice. In prenatally untreated as well as in TNBS-treated mice, thymocytes proliferating in the absence of nominal antigen were double negative (L3T4-/Lyt2-), but antigen-specific thymocytes were single positive (L3T4+/Lyt2- or L3T4-/Lyt2+). TNBS-treated mice differed from controls inasmuch as in their first week of life T cells proliferating in response to TNP were found in the thymus and detected at increased frequencies in the spleen. The frequency of TNP-specific thymocytes and spleen cells declined rapidly, finally reaching in the spleen a level of 20-30% of controls. Furthermore, after antigenic stimulation, the frequency of thymocytes and spleen cells proliferating in response to TNP was found to be increased in control mice, but TNP-specific T cell were no more recovered in the thymus or the spleen of tolerized mice. The same accounted for thymic and splenic T cells proliferating in response to Sp6. They were expanded in control mice after antigenic stimulation, but were undetectable in TNBS-treated mice. Thus, T cells with specificity for an internal (Sp6) and an external (TNP) antigen, provided the latter was present during ontogeny, were detected in the thymus of control and, transiently, in the thymus of tolerized mice. But, the fate of antigen-specific thymocytes was different in prenatally untreated and TNBS-treated mice. The data are interpreted in the sense that tolerance toward non-MHC antigens may be acquired subsequently to tolerance toward self-MHC antigens and possibly after imprinting of antigen specificity.