Self versus non-self carrier in primary and secondary anti-TNP B cell response: I. Specificity of help

Generation and characterization of T-helper cells by primary in vitro sensitization using Langerhans cells

We have utilized cultured Langerhans cells to activate and expand hapten- and protein-specific T-helper cells from nonsensitized mice. The generation of these lines was strongly dependent on eliminating all autologously reacting cells from the responder T-cell population. Primary in vitro sensitization was not uniquely induced with cultured Langerhans cells as splenic dendritic cells could subserve the same function. Despite its ability to induce strong allogeneic T-cell responses as well as hapten-specific secondary responses, M12c cells, a class II-bearing B-cell lymphoma line, could not activate hapten-specific T-helper cells in vitro. After primary or secondary in vitro stimulation, the T-helper cells which are generated secrete IL-2 and are able to adoptively transfer hapten-specific contact sensitivity, thus stimulating Type-1 T-helper cells. The T-helper cell lines which were generated after repeated cycles of stimulation stimulated type-2 T-helper cells in that they produced IL-4 and depended on this cytokine for autocrine growth. As well, when cultured with syngeneic, hapten-modified, small resting B cells, these T-helper cells caused specific IgE production. Thus, the studies reported herein demonstrate that it is possible to activate and expand T-helper cells with desired specificity from nonsensitized animals in vitro. Previous studies have demonstrated that expansion and adoptive transfer of effector T cells with specificity for tumor-associated antigens may be useful in the control of certain tumors; T-helper cells generated by in vitro sensitization should also be useful in adoptive immunotherapy.

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.

Characterization of primary T helper cell activation and T helper cell lines stimulated by hapten-modified, cultured Langerhans cells

It has recently been shown that hapten-modified cultured Langerhans cells are able to activate small resting syngeneic L3T4+ T helper cells from nonsensitized animals. Repeated stimulation of these T cells with hapten-modified cultured Langerhans cells leads to the establishment of L3T4+ hapten-specific interleukin-4-producing T-cell lines. Here we report on further characteristics of primary hapten-dependent activation of L3T4+ T cells and of T-cell lines derived from them. Dendritic cell-enriched spleen cells were as able as Langerhans cells to activate nonsensitized T helper cells after hapten modification. However, M12c, a major histocompatibility complex class II-positive B-cell line that was able to activate small, resting, allogeneic L3T4+ T cells was not able to stimulate syngeneic T helper cells after hapten modification. Thy1+ dendritic epidermal cells did not significantly affect the magnitude of primary T helper cell proliferation induced by cultured Langerhans cells. Restimulation of in vitro primed T helper cells with hapten-modified cultured Langerhans cells revealed the presence, within the primed T helper cell population, of activated cells with specificity to an unrelated hapten, suggesting that, in hapten-dependent T helper cell activation, hapten-nonspecific cells are activated along with those that are hapten specific. Restimulation of a hapten-specific long-term T helper cell subline using different antigen-presenting cell types demonstrates that factors other than major histocompatibility complex class II density or tissue derivation of the antigen-presenting cell play a role in the activation of T cells in vitro. Finally, we demonstrate that in vitro generated hapten-specific T helper cell lines may not show strict major histocompatibility complex restriction.