BASIS FOR THE ANTIGENICITY OF HAPTEN-POLY-L-LYSINE CONJUGATES IN RANDOM-BRED GUINEA PIGS

STUDIES ON ANTIGENICITY. THE RELATIONSHIP BETWEEN IN VIVO AND IN VITRO ENZYMATIC DEGRADABILITY OF HAPTEN-POLYLYSINE CONJUGATES AND THEIR ANTIGENICITIES IN GUINEA PIGS

The enzymatic degradation of fluorescein conjugates of poly-L-lysine, poly-D-lysine, and exhaustively succinylated poly-L-lysine by aqueous extracts of spleens from "responder" (guinea pigs which can develop immune responses to hapten-poly-L-lysine conjugates) and "non-responder" guinea pigs was investigated. The in vivo degradation of H³-tagged dinitrophenyl conjugates of these synthetic polyamino acids was also studied by measuring urinary excretion of radioactive low molecular weight degradation products of these conjugates after their intraperitoneal injection. It was found that both responder and non-responder guinea pigs can degrade succinylated and unsuccinylated poly-L-lysine conjugates into small molecular fragments, but they cannot degrade hapten-poly-D-lysine conjugates. These studies demonstrate that in addition to the known requirements for antigenicity of macromolecules, i.e. the presence of antigenic determinants, and their capacity to be degraded by immunological tissues, the resulting degradation products must undergo certain additional, as yet unidentified, specific metabolic steps in order to induce an immune response.

STUDIES ON DELAYED HYPERSENSITIVITY. I. INFERENCES ON THE COMPARATIVE BINDING AFFINITIES OF ANTIBODIES MEDIATING DELAYED AND IMMEDIATE HYPERSENSITIVITY REACTIONS IN THE GUINEA PIG

Experiments carried out with several well defined antigenic systems (hapten conjugates of poly-L-lysine and guinea pig serum albumin) in guinea pigs demonstrated that: 1. Arthus reactions also manifest carrier specificity, although to a smaller extent than do delayed hypersensitivity reactions. 2. Desensitization by injection of minute doses of antigen results in moderate specific desensitization of delayed hypersensitivity without desensitization of Arthus reactivity to the same antigenic determinant. 3. Insoluble antigen-antibody complexes prepared from high affinity guinea pig antibodies can elicit specific delayed skin reactions in sensitized guinea pigs. 4. Homologous conjugates of structurally similar haptens show considerably less cross-reactivity in delayed reactions than in immediate hypersensitivity reactions to the same antigenic determinant. These experimental results are interpreted as indicating that delayed hypersensitivity reactions in the guinea pig are mediated by "antibodies" of comparatively high binding affinities. High binding affinities are achieved for these antibodies more likely by closer structural adaptation between antigen and antibody than by a larger area of specific contact.

ANTIGEN-ANTIBODY REACTION: NATURE OF COMPLEX INITIATING DELAYED HYPERSENSITIVITY

Two homologous lightly coupled dinitrophenyl conjugates of poly-L-lysine of differing average molecular sizes were compared with regard to their abilities to elicit in guinea pigs specific delayed hypersensitivity skin reactions, passive cutaneous anaphylaxis, and active Arthus reactions. Equal concentrations by weight (but not equimolar concentrations) of the two conjugates elicited equally intense delayed hypersensitivity reactions and Arthus reactions, whereas equimolar concentrations (but not equal weightconcentrations) elicited equally intense passive cutaneous anaphylaxis reactions. These results suggest that delayed hypersensitivity reactions are initiated by the reaction of antigen with antibody molecules in true solution, and not by the simple bridging by antigen of a small number of antibody molecules firmly fixed to cell membrane surfaces. Whether "sensitized cells" or circulating "delayed hypersensitivity antibodies" are the specific mediators of the delayed hypersensitivity reactions is discussed.

The basis for the immunoregulatory role of macrophages and other accessory cells

Macrophages handle extracellular proteins and secrete diverse bioactive molecules and, therefore, influence the physiology of many tissues. They also have an important immunoregulatory role. The immune response to proteins involves the activation of the T helper subset of lymphocytes. The T helper cell is activated only when it interacts with the protein displayed on the surface of a macrophage or other accessory cell. This interaction involves restrictive proteins encoded in the major histocompatibility gene complex as well as growth-differentiating proteins.

Failure to find holes in the T-cell repertoire

The ability of an animal to respond to a given antigenic peptide depends on its major histocompatibility complex (MHC) type. Some peptides are not immunogenic when combined with a particular form of the MHC-encoded molecule. This non-responsiveness is regulated by immune response (Ir) genes and is thought to arise by one of two distinct mechanisms. Either the MHC-encoded molecules physically fail to interact with the antigen, preventing the activation of T cells with appropriate receptors, or they limit the expressed repertoire of T cell clones so that no T cells are available to be activated by existing complexes of MHC-encoded molecules and antigen. Experimental evidence has been generated to support both mechanisms. However, the relative importance of each has not been clearly established. In this study we started with a peptide that was immunogenic in B10 mice; it was thus known to be able to interact with the MHC molecule, and T cells existed which could recognise the peptide-MHC complex. Based on previous experiments, we then changed only those parts of the peptide that we thought interacted with the T-cell receptor. All the new analogues created were still immunogenic, confirming that the amino-acid substitutions that we had made did not prevent productive interactions with the MHC-encoded molecule. No limitations ('holes') in the T-cell repertoire were found. The experiments demonstrate the vast potential of the T-cell population to recognize many different analogues, each in a unique way, and suggest that constraints on the diversity of the T-cell repertoire may not be a major explanation for Ir gene defects.

Fact and speculation on the function of immune response genes in antigen presentation

Immune responsiveness of guinea pigs to dinitrophenyl-poly-L-lysine and to the lysine rich random co-polymer of L-glutamic acid and L-lysine are both controlled by a single gene, the 'poly-L-lysine gene'. This paper reviews recent experiments which demonstrate that these two antigens specifically compete with one another for being presented to T cells by the same antigen-presenting cells. This finding is interpreted to mean that antigens to which responsiveness is controlled by the same single gene compete for the Ir gene product of antigen-presenting cells. The review discusses if the products of the immune response genes-presumable the Ia antigens-may constitute a third specific antigen recognition system. It further speculates if this idea may help to provide insight into the phenomenon of histocompatibility-restriction and into the nature of the mixed leucocyte reaction.

Genetic control of the immune response to ferritin in mice

The immune response to the antigen horse spleen ferritin was tested in sixteen inbred strains of mice. Using a fixed antigen percentage bound isotope technique, it was found that the quantity of antibody produced was related to the genetic status of the responding animal. A continuous distribution of responses was obtained, which were found to be linked to H-2 loci and the 2 non-H-2 loci 'Tla' and 'Theta' and these responses are detectable following primary immunization. It is suggested that the continuous distribution of quantitative antibody responses to ferritin, is compatible either with a large number of IR-genes or with a cross tolerance hypothesis requiring no IR-genes at all.

Specific immune response genes of the guinea pig. V. Influence of the GA and GT immune response genes on the specificity of cellular and humoral immune responses to a terpolymer of L-glutamic acid, L-alanine, and L-tyrosine

The ability of guinea pigs to make immune responses to the random linear copolymer of L-glutamic acid and L-alanine, GA, and to L-glutamic acid and L-tyrosine, GT, is each controlled by a different immune response gene. On the other hand, the random linear terpolymer of L-glutamic acid, L-alanine, and L-tyrosine, GAT, which contains both GA and GT antigenic determinants, is immunogenic in all guinea pigs. After GAT immunization, all animals develop delayed hvpersensitivity and serum antibody specific for GAT. However, only those guinea pigs possessing the GA immune response gene demonstrate cross-reactive delayed hypersensitivity when challenged with GA. In addition, the anti-GAT antisera produced by those animals having the GA gene contain cross-reacting anti-GA antibodies. The sera from guinea pigs lacking the GA gene have no anti-GA antibody activity. Thus, we have demonstrated that a specific immune response gene controlling responsiveness to a "simple" antigen can determine the specificity of both cellular and humoral immune responses to a more complex antigen.

Antigen recognition and antibody specificity. Carrier specificity and genetic control of anti-dinitrophenyl-oligolysine antibody

The exact specifiicity of anti-DNP antibody produced by Hartley guinea pigs immunized with a series of defined alpha,DNP and epsilon,DNP-oligolysines was studied by fluorescence quenching. All responder animals made anti-DNP antibody which recognized the precise chain length, +/- 1 lysyl residue, of the DNP-oligolysines used to induce the immune response as measured by an increase in binding energy (-DeltaF degrees ) for that antigen. The ability of the immune system to detect the smallest possible change in oligolysine chain length suggests that the anti-hapten antibody-forming cell possesses a highly specific recognition system for carrier conformation. When DNP-oligolysines are incorporated in an adjuvant containing M. tuberculosis H37Rv, both responder and nonresponder produce anti-DNP antibody, but only the responder develops delayed skin sensitivity. In addition to their failure to develop delayed hypersensitivity, nonresponders produced anti-DNP oligolysine antibody which did not show the increase in -DeltaF degrees for the immunizing antigen characteristic of responder antibody. These observations support a local environment hypothesis for antigen recognition at the level of the anti-hapten antibody-forming cell and suggest that the polylysine gene exerts its control at the same cell.

Carrier function in anti-hapten immune responses. I. Enhancement of primary and secondary anti-hapten antibody responses by carrier preimmunization

Preimmunization of either guinea pigs or rabbits to bovine gamma globulin (BGG) prepares the animals for markedly enhanced antibody responses to 2,4-dinitrophenyl-BGG (DNP-BGG). This phenomenon is observed both in the primary anti-DNP antibody response to DNP-BGG and in the secondary anti-DNP antibody response to DNP-BGG in animals primed with DNP-ovalbumin (DNP-OVA). The BGG preimmunization is most effective if the antigen is administered as a complete Freund's adjuvant emulsion; in rabbits, a dose of 1 microg of BGG is more effective than a dose of 50 microg, whereas the reverse is true in guinea pigs. Transfusion of homologous anti-BGG sera fails to replace active immunization with BGG in the preparation of animals for these enhanced anti-DNP antibody responses. Both the immunoglobulin class and the average association constant for epsilon-DNP-L-lysine of the anti-DNP antibody produced in these enhanced responses is determined by the mode and time of immunization with haptenic conjugates and is not appreciably influenced by the nature of the carrier preimmunization. These studies indicate that the carrier specificity of hapten-specific anamnestic antibody responses is largely due to the interaction of two independent cell associated recognition units, one specialized for carrier and the other specific for haptenic determinants.

Antigen recognition: in vitro studies on the specificity of the cellular immune response

Studies of the immunochemical specificity of antigen-induced thymidine-2-(14)C incorporation in lymph node cells obtained from animals immunized to a series of closely related alpha-DNP-oligolysines, epsilon-DNP-oligolysines, and oligolysines have shown that the sensitized cell exhibits an extraordinary degree of specificity for antigen. The sensitized cell is maximally stimulated by the homologous immunizing antigen and can discriminate among compounds which differ from one another only in the position of a dinitrophenyl group or D-lysine residue on an identical oligolysine backbone. These studies support the view that the immunogen is not degraded prior to the induction of the immune response, and that the majority of cells produced as a consequence of immunization have stereospecific antigen receptors for the DNP-oligolysine used to induce the response; a smaller and more variably sized population of cells is produced with receptors specific for the oligolysine portion of the immunizing antigen. When specifically sensitized lymph node cell cultures are stimulated in vitro by heterologous DNP-oligolysines, the oligolysine- and not the DNP-oligolysine-sensitive population of cells appears to play a crucial role in the specificity of such cross-reactions. It is concluded from these studies that the antigen receptor on the sensitized lymph node cell differs in both kind and degree from conventional antibody. The chemical nature of the receptor and the means by which this receptor reacts with antigen to initiate the biosynthetic or proliferative cellular immune response still remain undefined.

The nature of the antigenic determinant in a genetic control of the antibody response

The response of inbred mouse strains to two polypeptides derived from multichain polyprolines, (T,G)-Pro--L and (Phe,G)-Pro--L, is different from the response of the same mouse strains to a similar series of polymers built on multi-poly-D,L-alanyl--poly-L-lysine, although the same short sequences of amino acids are attached to the side chains of the polypeptides in the two series. These results indicate that a portion of the side chain (e.g. polyalanine or polyproline) participates in the antigenic determinant. This was confirmed by studying the response of different mouse strains to two kinds of polypeptides: (T,G)-Pro-A--L 717 and 718 and (T,G)-A-Pro--L 719 and 721. Antibody assay of antisera to (Phe,G)-Pro--L with the cross-reacting antigens (T,G)-Pro--L and (Phe,G)-A-L indicates that different inbred mouse strains make antibodies specific for different parts of the same polypeptide. Thus, antibody from DBA/1 mice reacts almost exclusively with the (Phe,G) sequence, while SJL antisera bind only (T,G)-Pro--L and fail to bind (Phe,G)-A-L. The immune responses to the same amino acids on two different polypeptides (i.e. A--L and Pro--L) appear to be under separate genetic control.

The behavior of hapten-poly-L-lysine conjugates as complete antigens in genetic responder and as haptens in nonresponder guinea pigs

30 to 40% of Hartley strain guinea pigs have previously been demonstrated to possess a dominant autosomal gene which enables them to recognize the antigenicity of hapten-poly-L-lysine conjugates as expressed by the development of both antihapten antibodies and delayed hypersensitivity to the immunizing antigen. In the present study, it was shown that PLL alone was weakly antigenic in such genetic responder animals. Immunization with DNP-PLL electrostatically combined with foreign albumins elicits the production of anti-DNP antibodies in all Hartley strain guinea pigs, although the percentage of animals demonstrating a delayed response to DNP-PLL and therefore considered genetic responders remains 30 to 40%. Immunization with nonantigenic polyanions combined with DNP-PLL does not produce such an effect. Some degree of PLL specificity of purified anti-DNP antibodies produced by genetic nonresponder animals by immunization with DNP-PLL combined with foreign albumins was demonstrated by means of fluorescence quenching.

Genetic control of combining sites of insulin antibodies produced by guinea pigs

1. Genetic factors control the configuration of combining sites of guinea pig insulin antibodies. 2. It is possible that the configuration of the combining sites of guinea pig insulin antibodies is controlled by more than one gene and not by multiple alleles at a given gene locus.

Genetic control of the antibody response. I. Demonstration of determinant-specific differences in response to synthetic polypeptide antigens in two strains of inbred mice

Immunization of CBA and C57 mice with a branched, multichain synthetic polypeptide, poly (tyr,glu)-poly DL-ala--poly lys, ((T,G)-A--L), in Freund's complete adjuvant results in a tenfold or more difference in the antigen-binding capacity of sera from the two strains, although they respond equally to bovine serum albumin. Immunization of CBA x C57 F(1), F(1) x CBA, and F(1) x C57 mice reveals definite genetic control of the response to (T,G)-A--L, which appears to be due to a single major genetic factor, with perhaps one or more modifying factors. Immunization of CBA and C57 mice with (H,G)-A--L, a synthetic polypeptide in which histidine replaces tyrosine, gives the opposite result, CBA's respond and C57's do not. From this, it appears that the genetic control of the response to (T,G)-A--L is specific for the antigenic determinant. The implications of these results are discussed.

GENETIC CONTROL IN GUINEA PIGS OF IMMUNE RESPONSE TO CONJUGATES OF HAPTENS AND POLY-L-LYSINE

Random-bred Hartley strain guinea pigs which do not respond immunologically to conjugates of hapten and poly-L-lysine mere mated with heterozygous guinea pigs which do. These responders were considered heterozygous for this trait since their mating resulted in at least one nonresponder offspring. Of 31 offspring from 10 breeding pairs (nonresponder x heterozygous responder) 14 were responders. There was no evidence that this trait is sex-linked. This finding confirms the view that, in guinea pigs, development of an immune response to the aforementioned conjugates is a genetically transmitted autosomal, unigenic Mendelian dominant trait.