Reconstitution of genetically regulated responses against random and ordered synthetic polypeptides by methylated bovine serum albumin as analyzed by isoelectric focusing

Clonotypic analysis of the antibody response to the acetylcholine receptor in experimental autoimmune myasthenia gravis

Autoreactive B cells reactive with the acetylcholine receptor (AChR), and the antibodies produced by them, are proposed to play a primary role in the immunopathology of myasthenia gravis and its animal models. Therefore, the anti-AChR antibody response induced in rats was characterized for the clonotypic heterogeneity, isotype distribution, and affinity by isoelectric focusing (IEF) and affinity immunoblotting. It was determined that the rat anti-AChR serum antibody was relatively heterogeneous, reflecting the oligoclonality of the response. Furthermore, isotypic dominance by IgG2a was observed in that the majority of clonal products detected by IEF were of this isotype in both primary and secondary responses. Lastly, the clonotypic anti-AChR antibodies were of relatively low affinity (avidity) when compared to antibodies reactive with the highly immunogenic protein antigen, keyhole limpet hemocyanin; anti-AChR antibody avidity did not appear to increase when the antibodies in the secondary response were compared to antibodies in the primary response. These antibody characteristics are discussed in terms of their role in disease induction.

Influence of T cell specificity on the heterogeneity and disease-causing capability of antibody against the acetylcholine receptor

Adoptive secondary anti-acetylcholine receptor (AChR) antibody responses were examined in rats to evaluate the influence of helper T cell specificity on the nature and disease-causing potential of antibody produced. Mixtures of B cells reactive with the intact AChR plus T cells reactive with purified AChR subunits (alpha, beta, gamma, delta) were transferred and antigen-challenged in immunologically naive recipient rats; the serum anti-AChR antibody produced was assessed by radioimmunoassay for differences in titers and by isoelectric focusing for differences in clonal heterogeneity as a function of the subunit specificity of T cells transferred. In addition, rats receiving different sources of AChR or AChR subunit-reactive T cells were examined for AChR-dependent muscle dysfunction. The results indicated a clear reduction in anti-AChR antibody concentrations and clonal heterogeneity in recipient rats receiving T cells of specificities restricted to individual subunits. However, except for a clear relationship between serum anti-AChR antibody concentration and disease induction, no particular AChR subunit-reactive helper T cell specificity appeared to preferentially cause muscle dysfunction. We conclude that if such relationships exists, T cells with specificities more restricted than those described here will have to be used.

Liposomes as immunological adjuvants in eliciting antibodies specific to the synthetic polypeptide poly(LTyr, LGlu)-poly(DLAla)--(LLys) with high frequency of site-associated idiotypic determinants

The antibody response to the synthetic polypeptide, poly(LTyr, LGlu)-poly(DLAla)--poly(LLys), [(T,G)-A--L], injected entrapped in liposomes which served as adjuvant has been analyzed. The liposomes used were composed of phosphatidylcholine, cholesterol, dicetylphosphate and DL alpha-tocopherol (molar ratios as 4:3:0.1:0.5) and therefore, were negatively charged. Since the (T,G)-A--L is also negatively charged, no free complexes were formed. The (T,G)-A--L was found to be entrapped inside the enclosed volume of the liposomes, and no (T,G)-A--L antigenic determinants could be detected on the liposomal membranes. Injection of high-responder C3H.SW (H-2b) mice with (T,G)-A--L-bearing liposomes demonstrated that the i.p. and the i.v. routes of immunization were efficient in eliciting (T, G)-A--L specific antibodies, whereas the i.d. injection led to poor antibody responses. The latter route of immunization is the most effective when (T,G)-A--L is injected in complete Freund's adjuvant (CFA). When low doses (0.1 and 1 microgram) of (T, G)-A--L were used for immunization, the liposomes were better adjuvants than CFA. The effectiveness of the liposomes as immunological adjuvants was also shown in their ability to induce high-potential, primed memory cells. The pattern of low (H-2k,a) and high (H-2b) responsiveness to (T,G)-A--L was retained following immunization with (T,G)-A--L entrapped in liposomes, as tested in two pairs of congenic strains. (T,G)-A--L-specific antibodies induced by injection with 1 microgram antigen entrapped in liposomes bear the (T,G)-A--L site-related idiotypic markers of C3H.SW (Igh-1a) mice in a significantly higher frequency than the homologous idiotypes, namely the antibodies elicited in this strain against (T,G)-A--L in CFA. Thus, liposomes may serve as adjuvants for the production of relatively restricted (T,G)-A--L-specific antibodies of high quality.

Efficient genetically controlled formation of antibody to a synthetic antigen [poly(LTyr, LGlu)-poly(DLAla)- -poly(LLys)] covalently bound to a synthetic adjuvant (N-acetylmuramyl-L-alanyl-D-isoglutamine)

The synthetic polypeptide antigen poly(LTyr, LGlu)-poly(DLAl)- -poly(LLys)[T,G)-A- -L] was covalently linked to N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), which is the minimal adjuvant-active structure that can substitute for Mycobacteria in complete Freund's adjuvant. When injected in aqueous solution into mice, the completely synthetic conjugate elicited significant antibody responses specific to (T,G)-A- -L, whereas (T,G,)-A- -L alone administered under the same conditions did not lead to antibody production. The conjugate was much more efficient in eliciting (T,G)-A- -L responses than was a mixture of DMP and (T,G)-A- -L. One hundred micrograms of MDP mixed with 10 micrograms of (T,G)-A- -L resulted in production of (T,g)-A- -L-specific antibodies. However, the titers obtained were much lower than those observed with 10 micrograms of the conjugate, MDP-(T,G)-A- -L, which contained less than 1 microgram of MDP. MDP was enhanced when the mixture was administered in incomplete Freund's adjuvant, the adjuvant did not significantly affect the (T,G)-A- -L-specific antibody responses in mice immunized with MDP-(T,G)-A- -L. The isoelectric focusing pattern of antibodies obtained with MDP-(T,G)-A- -L was similar to that obtained after immunization with (T,G)-A- -L in complete Freund's adjuvant. The pattern of high-responder and low-responder mice to (T,G)-A- -L, the immune response to which is genetically controlled, was retained when MDP-(T,G)-A- -L was used as the immunogen. Conjugation of (T,G)-A- -L was creased the immunogenicity of MDP and affected its biological properties. It is thus possible to obtain efficient immune responses to synthetic polypeptide antigens that produce poor reactions when injected in aqueous solution by conjugating them to small molecular weight synthetic adjuvants.

Genetic control of the immune response to the terpolymer L-glutamic acid 60-L-alanine 30-L-tyrosine10 (GAT). III. Restricted heterogeneity of the anti-GAT response from BALB/c responder mice

The heterogeneity of the anti-GAT [terpolymer poly(Glu60, Ala30, Tyr10)] response of GAT responder mice has been analyzed. Purified anti-GAT antibodies from BALB/c mice belong only to the gamma 1 kappa subclass. The isoelectric focusing pattern obtained indicates that the anti-GAT antibodies are particularly basic and restricted. These results have been confirmed by two-dimensional polyacrylamide gel electrophoresis; by this technique, we have shown that the gamma 1 chain and the corresponding kappa chain of anti-GAT antibodies are restricted. All the anti-GAT antibodies from 10 BALB/c mice bear the cross-reactive GAT idiotype previously defined (J. Thèze and G. Sommé, Eur. J. Immunol. 1979, 9: 924). The present results indicate that the anti-GAT repertoire expressed in BALB/c mice is very limited.

Identification of different antigenic determinants within the synthetic multichain Co-polymer poly(LTyr,LGlu)-poly(DLAla) -- poly (LLys), (T,G)-A--L, as recognized by the chicken. II. Fine-specificities of the anti-(T,G) part of chicken anti-(T,G)-A--L antisera

Sera from three chickens obtained from a genetic high-responder inbred strain immunized with the multichain polypeptide poly(LTyr,LGlu)-poly-(DLAla)--poly(LLys) (T,G)-A--L) were analysed for possible restrictions in the fine-specificities of anti-(LTyr,LGlu) antibodies. A panel of synthetic hexa- and heptapeptides composed of L-Tyr and L-Glu residues linked to a C-terminal spacer tripeptide, and with L-Tyr as N-terminal, were used as inhibitors in a double-antibody radioimmunoassay. Results showed that all peptides tested possessed some inhibitional potential, although the percentage of displacement for the different sequences varied between 43% and 58%,20% and 56%, and 48% and 85%, respectively, for the three sera tested at a given inhibitor concentration. Different peptide sequences appeared as the most efficient inhibitor in the three sera tested. No simple relationship was found between substitution/elongation of inhibitor peptides and their inhibitional potential, as would have been expected from a simple conception of (T,G)-A--L possessing only one sequential determinant. Possible evidence for conformational determinants in the (T,G)-A--L antigen is discussed.

The nature and functions of specific immune response genes and their products

Antibodies produced by inbred mouse strains immunized with the random synthetic polypeptide poly (Tyr,Glu)-poly(DLAla)--polyLys denoted (T,G)-A--L were found to be specific mainly to the ordered peptide Tyr-Tyr-Glu-Glu. Low responder H-2k mice, upon immunization with either the random (T,G)-A--L or the ordered (T-T-G-G)-A--L coupled to methylated bovine serum albumin (MBSA), produce antibodies with comparable titers to those observed in high responder H-2b mice following immunization with the antigens alone or with their complexes with MBSA. A comparison of the above antibodies have led to the conclusion that low responder mice, upon immunization with the synthetic antigens complexed with MBSA, produce antibodies of the same specificity and quality as those of high responders (as shown by the isoelectric focusing technique) and they also have the same affinity and heterogeneity as antibodies of H-2b mice (measured by equilibrium dialysis and antigen binding capacity assay). Anti-idiotypic sera to anti-T,G)-A--L antibodies of C3H.SW (H-2b,Ig-1a) mice were raised in guinea pigs. C3H.SW anti-(T,G)-A--L antibodies from different pools cross reacted idiotypically. Anti-(T,G)-A--L antibodies of CWB (H-2b, Ig-1b) mice did not react with the anti-idiotypic serum suggesting linkage between the genes coding for idiotypes and allotypes. C3H/DiSn (H-2k, Ig-1a) anti-(T,G)-A--L antibodies elicited by immunization with (T,G)-A--L complexed to MBSA reacted with the anti-idiotypic serum to the same degree as C3H.SW anti-(T,G)-A--L antibodies, confirming the similarity between the high and low responder anti-(T,G)-A--L antibodies. C3H.SW (H-2b) mice as well as C3H/DiSn (H-2k) mice were found to be capable of producing an antigen specific factor from "educated" T cells which replaces the helper effect of T cells in the process of antibody production. On the other hand B cells of H-2k mice were not triggered by a factor of either high or low responder specific T cells. The activity of a C3H.SW (T,G)-A--L specific T cell factor was removed after passage on a Sepharose column coupled to the anti-idiotypic serum prepared against C3H.SW anti-(T,G)-A--L antibodies, suggesting similarity between the antigen specific T cell factor and the B cell recognition system. A (T,G)-A--L specific factor produced by C3H/DiSn (H-2k, Ig-1a) "educated" T cells reacted with the anti-idiotypic serum as well. Thus, C3H.SW high and C3H/DiSn low responder (T,G)-A--L specific T cell factors cross react at the level of their binding site for antigen.

Presence of common idiotypes on antibodies induced by glutamic acid-lysine-containing terpolymers in responder and nonresponder mice with the Ig-1b heavy chain allotype

A B10.A (5R) responder mouse to the random linear terpolymer, poly--(Glu, Lys, Phe), GLphi, can produce immunoglobulins which bind poly-L (Glu, Lys), GL, that share idiotypic determinants with GL-binding antibodies produced by other members of the same strain. Expression of these common idiotypic determinants, termed BGL, is independent of the H-2 halotype and closely linked to the Ig-lb heavy chain allotype. Moreover, nonresponder mice with the Ig-lb heavy chain allotype, when immunized with GLphi that has been chemically coupled to an immunogenic carrier, chicken IgG, can produce GL-binding antibodies that share BGL idiotypic specificities with anti-GLphi antibodies produced by responder animals. Also, the responses to other GL-containing polymers, such as poly-L (Glu, Lys, Ala) and poly-L (Glu, Lys, Pro), which are under the control of distinct Ir genes, can stimulate the production of GL-binding antibodies that share common BGL idiotypic determinants with antibodies induced with GLphi. These findings are discussed with respect to their implications concerning the mechanism(s) of Ir gene control.

Physicochemical studies of a branched polypeptide antigen: poly(L-Tyr,L-Glu)-poly(DL-Ala)--poly(L-Lys)

The synthesis of a branched polypeptide, poly(L-Tyr,L-Glu)-poly(DL-Ala)--poly(L-Lys), is described. Physicochemical investigations of the polymer by means of hydrogen-deuterium exchange, potentiometric titrations, and viscosity measurements indicate a non-ordered, flexible conformation in aqueous solution, depending on pH and salt concentration. A hysteresis phenomenon observed in the titrations is tentatively ascribed to interactions between the sidechains, and in accordance with observations from the infrared spectrum of the polymer it is suggested that rather slow conformational changes of the polymer molecules occur in aqueous solutions. The immunochemical implications of the physiochemical findings are discussed with special reference to the concept of sequential and conformational determinants.