Lise Leclercq

Monoclonal anti-gat antibodies with different fine specificities express the same public idiotype☆

We have studied the idiotypic specificities expressed by 22 anti-GAT hybridoma products (HP). These antibodies, although derived from cells of mice with three distinct heavy-chain linkage groups (BALB/c, Igh-1a, DBA/2, Igh-1c and C57BL/6, Igh-1b) all express the same public idiotypic specificity, p. GAT, defined by the heterologous binding of anti-idiotypic serum 715 to C57BL/6 anti-GAT antibodies. None of these antibodies expressed the strain-restricted idiotypic specificity, s.r. GAT-1, defined by the binding of anti-idiotypic serum JL 122 to BALB/c anti-GAT antibodies. BALB/c anti-GAT HP could be shown to fall into three subsets with respect to their fine antigenic specificity for GAT, GT and GA. An individual idiotypic specificity, i1-GAT (defined by syngeneic anti-idiotypic sera raised against one of the BALB/c HP), was also found on a group of BALB/c HP which all shared a similar fine antigenic specificity pattern. Taken together, these observations suggest that the expressed mouse anti-GAT repertoire derives from a very few V-germ-line genes (VH-GAT and VK-GAT) which are highly conserved in the species, and which determine the structure resulting in the p. GAT idiotypic specificity. The variations in fine specificity and individual idiotype are likely therefore to reflect somatic variations affecting these germ-line genes.

Contribution of the H- and L-chains and of the binding site to the idiotypic specificities of mouse anti-GAT antibodies

The contribution of the H- and L-chains to the structure of the main idiotype of anti-poly (Glu60-Ala30-Tyr10) (GAT) antibodies has been studied. This idiotype has been previously divided into four types of specificity: (1) the highly conserved idiotypic specificity (h.c. GAT) is expressed by anti-GAT antibodies from the guinea-pig, rat and mice; (2) the public specificity (p. GAT) is expressed in an identical form by all anti-GAT antibodies from all strains of mice tested and by all hybridoma products (HP) with anti-GAT activity; (3) the strain-restricted specificity (s.r. GAT-1) is only expressed by anti-GAT antibodies from strains with Ig-1a, Ig-1c and Ig-1c allotypic markers; and finally (4) the individual specificity i1-GAT defined on HP G5 is also expressed by most of the hybridoma protein with anti-poly (Glu50-Tyr50) (GT) activity. In this paper we show that h.c.GAT, p.GAT and i1-GAT require the interaction of H- and L-chains to be expressed: (1) isolated H- and L-chains from HP G5 did not express these specificities; and (2) recombinant molecules composed of H- and L-chains from HP with anti-GAT activity and an irrelevant myeloma protein (MOPC21) never expressed h.c.GAT, p.GAT and i1-GAT. We next investigated the relationship between the GAT binding site and the p.GAT, h.c.GAT and s.r.GAT-1 idiotypic specificities. GAT and GT were not able to inhibit the binding to s.r.GAT-1 while they inhibit the idiotypic binding to p.GAT and h.c.GAT. A GAT fragment of mol. wt 3000 was also shown to inhibit the binding of p.GAT and h.c.GAT to the appropriate sera. Thus p.GAT and h.c.GAT are very close to the GAT combining site while s.r.GAT-1 represents an idiotypic specificity located outside the GAT binding site.

In vitro induction and expression of interleukin 2 receptor in a clonal T helper cell differentiation model

Induction and expression of interleukin 2 (IL 2) receptor have been studied using a poly( Glu60 Ala30 Tyr10 ) (GAT)-specific T cell clone of mouse origin. This clone (52-3) has been characterized and it exhibits functional properties of T helper (TH) cells: it leads to a specific anti-DNP response in the presence of DNP-GAT and DNP-primed B cells and it secretes biological activities which can induce polyclonal B cell proliferation and IgM secretion. In vitro this clone mimics the activation stages of normal T lymphocytes and can be obtained under two states of differentiation. depending on the antigen-specific signal provided by antigen-presenting cells (APC). The expression of IL 2 receptor by this clone has been studied by (i) its response to IL 2, (ii) its capacity to absorb IL 2 bioactivity, and (iii) its reactivity with monoclonal antibody 7D4 specific for mouse IL 2 receptor. All the results indicate that the unstimulated state does not express the IL 2 receptor while the activated state does. Clone 52-3 has been compared with clone 14-1.6 that derives from a TH cell line and expresses the IL 2 receptor constitutively. 52-3 offers a good experimental model for studying in vitro, in a clonal TH cell population, the detailed mechanism of IL 2 receptor induction.

In vitro inhibition of the helper activity of GAT-specific T-cell lines by a syngeneic anti-idiotypic serum: Preferential effect on the IgG1 response

Abstract We described in this paper the characteristics of a syngeneic anti-idiotypic serum made in BALB/c against BALB/c anti-poly (Glu 60 Ala 30 Tyr 10 ) (GAT) antibodies. This serum recognizes idiotypic determinants present in all anti-GAT sera whatever the allotypic markers of the mice used to prepare the sera. The functional effect of this serum on two helper cell lines is also described. Cell line BDF 1 /52 was obtained from GAT immunized lymph node cells (LNC). Cell line BDF 1 /E 3 was selected from splenic T-cells educated in vitro on GAT-pulsed adherent cells. Both lines were propagated in presence of filler cells, antigen, and medium containing T-cell growth factor(s) from splenic cells activated with concanavalin A. Both cell lines exhibit a helper activity as measured by the plaque-forming cell (PFC) response they induce in vitro in the presence of DNP-GAT and DNP sensitized B cells. Their helper activity is specific and they require a hapten-carrier bridge to activate B cells. These lines are able to induce IgG 1 , IgG 2a and IgG 2b anti-TNP PFC. Syngeneic anti-idiotypic serum B 658 inhibits specifically the function of these two lines but does not affect the helper activity of an OVA-specific T-cell line. The blocking activity of the serum can be adsorbed on a hybridoma protein with anti-GAT activity. This inhibition affects more dramatically the IgG 1 response than the IgG 2a and IgG 2b responses.

Supernatant from a cloned helper T cell stimulates resting B cells to express transferrin and IL-2 receptors

We describe the properties of the supernatant from a murine cloned helper T cell (clone 52.3) which is able to polyclonally activate most resting B cells in the absence of any additional stimulus. We hypothesize that an activity which we call BCAF (B-cell-activating factor(s] exists in our supernatant which can activate resting B cells alone or in conjunction with other lymphokines. In the present report, we investigate changes in the surface antigen pattern induced on resting B cells by BCAF-containing supernatant. Analysis of the cells by flow cytometry shows that transferrin receptor and IL-2 receptor expression increase on a large fraction of B cells after 2 days of activation by the T-helper-cell clone supernatant. Monoclonal anti-transferrin receptor antibody inhibits cell division but does not affect blastogenesis, while IL-2 has no effect in our experimental system. Our present results confirm that BCAF-containing supernatants can act on most resting B cells and replace helper T cells in inducing B-cell activation and proliferation.

Idiotype expression and fine specificity of Glu60Ala30Tyr10-specific T proliferating cells

The fine specificity of anti-Glu60Ala30Tyr10 (GAT) and anti-Glu60Ala40 (GA) proliferating cells was studied. T cells primed with GAT proliferate both to GAT and GA and GA-primed T cells proliferate also to GA and GAT. This cross-reactivity was unexpected given the results previously reported on the fine specificity of anti-GAT antibodies. The effect on the proliferation of BALB/c lymph node cells (LNC) of a syngeneic anti-idiotypic serum, prepared in BALB/c against anti-GAT antibodies, was studied. Two major points are made in this paper: (i) the in vitro addition of the anti-idiotypic serum in cultures containing GAT-primed LNC and GAT enhances the proliferation of GAT-specific T cells; (ii) the anti-idiotypic serum is effective in priming in vivo LNC which then acquire the capacity to proliferate specifically with GAT in vitro. These results further confirm the existence of idiotype-like determinants on T cells.

Analysis of a major rat idiotype associated with Anti-GAT antibodies.

An anti-idiotypic antiserum was raised in a rabbit against a pool of purified F.344 rat anti-GAT antibodies. GAT-13, the idiotype defined by this serum, is present in all F.344 anti-GAT sera from primary and secondary anti-GAT responses. Anti-GAT sera of 13 inbred rat strains, with different RT1 haplotypes and with different heavy- and light-chain allotypes, all express idiotypic determinants cross-reacting with GAT-13. Thus, like in mice anti-GAT antibodies from rats express public idiotypic determinants. The anti-idiotypic serum also recognizes a highly conserved idiotypic specificity present on mouse and guinea-pig anti-GAT antibodies. The mouse, rat and guinea-pig express a similar highly conserved idiotypic specificity after immunization with GAT. All anti-GAT antibodies from the mouse and guinea-pig bear this idiotypic specificity. These results confirm the existence in the anti-GAT response of interspecies cross-reactive idiotypic determinants.

Regulation of IgM expression by adjuvant activated splenic suppressor T cells

Adjuvant-activated Lyt-2 positive suppressor T cells (Ts) are able to inhibit the expression of IgM plaque-forming cells (PFC) during a primary in vitro response to sheep red blood cells. Under the same experimental conditions these suppressor T cells do not affect a secondary IgM PFC response against SRBC. Activated Ts cells were also found to suppress the spontaneous IgM secretion of cultured B cells as well as the IgM production of B cells stimulated by lipopolysaccharide or by supernatant from a T-helper-cell clone.

T Helper Cell Control of B Cell Development and Isotype Expression

The supernatant of the T helper cell clone 52.3 (52.3-SN) was shown to induce polyclonal activation of resting B cells. 52.3-SN acts on most small B cells and through the allogeneic barrier. This supernatant induces cell size increase, RNA and DNA synthesis, and appearance of interleukin-2 and transferrin receptor. These results are interpreted as indicating the existence of a B Cell Activating Factor (BCAF) acting on resting B cells in an MHC-unrestricted way.TH cells can be obtained in an intermediate state of activation where they secrete lymphokines leading to B cell proliferation and not the biological activities leading to plasmocyte development. TH cell clones can induce sIgG− and sIgA− unprimed B cells to switch and express all classes and subclasses of immunoglobulin. The bulk of the response consists of IgM. Among the non IgM isotypes, IgG1 and IgA predominate. The supernatants prepared from TH cells reproduce these effects.

Public idiotopes and/or internal images in the anti-poly(Glu60 Ala30 Tyr10) response: Analysis by monoclonal antibodies

From BALB/c mice immunized with BALB/c polyclonal anti-GAT antibodies, we have obtained monoclonal antiidiotypic antibodies directed against public idiotopes expressed following GAT (Glu60Ala30Tyr10) immunization in all individuals of all mouse strains tested. Nine monoclonal anti-Id antibodies were studied in detail. One of these monoclonals recognizes only polyclonal anti-GAT antibodies; the other eight recognize polyclonal anti-GAT antibodies and monoclonal anti-GAT antibodies. The distribution of the structures recognized by the different monoclonal anti-Id on a battery of twenty monoclonal anti-GAT antibodies allows a definition of two families of public idiotopes. The significance of the existence of these two families is discussed in light of the hypothesis recently proposed by Jerne et al. (EMBO J., 1982, 1, 243-247) who consider that the induction of internal images of antigen during immunization leading to the production of antiidiotypic reagents is responsible for the existence of public idiotopes. Our present results may be interpreted to indicate that even though certain monoclonal anti-Id reagents could be internal images of the antigen, the others do, in fact, recognize public idiotopes. Therefore, the notion of internal image does not exclude the existence of public idiotypic specificities.