Genetic control of immune responses

Fine specificity of antibodies to the synthetic polypeptide poly(L-tyrosine, L-glutamic acid)-poly(DL-alanine)--poly(L-lysine) and its ordered analogs as followed by solid-phase radioimmunoassay

The fine specificity of antibodies against (T,G)-A--L and its ordered analogs (T-T-G-G)-A--L and (T-G-T-G)-A--L was studied. Fifty percent of the antibodies against (T,G)-A--L are directed toward the T-T-G-G determinants and 19% against T-G-T-G-like determinants. The rest of the antibody response to (T,G)-A--L is directed against determinants which exist in (T,G)-A--L but are not cross-reactive with either T-T-G-G- or T-G-T-G-like determinants. Although (T-T-G-G)-A--L and (T-G-T-G)-A--L differ only in the sequence of tyrosine and glutamic acid in their side chains, no crossreactivity was observed between antibodies toward the two ordered polypeptide antigens.

Cellular analysis of specificity of antibodies and of delayed type hypersensitivity responses toward some structurally related synthetic antigens: boosting is determined by specificity of T cells

The crossreactivity between the random synthetic polypeptide antigen poly(Tyr,Glu)-poly(DLAla)--poly(Lys) [(T,G)-A--L] and its ordered-sequence analogs (Tyr-Tyr-Glu-Glu)-poly(DLAla)--poly(Lys) [(T-T-G-G)-A--L] and (Tyr-Glu-Tyr-Glu)-poly(DLAla)--poly(Lys) [(T-G-T-G)-A--L] at the level of humoral and cellular responses was studied. For delayed type hypersensitivity responses, (T,G)-A--L-activated T cells could be challenged with the homologous antigen as well as with the ordered analogs. T cells activated by (T-T-G-G)-A--L could be challenged with either the homologous antigen or with (T,G)-A--L but not with (T-G-T-G)-A--L. Similarly, no cross stimulation was observed between (T-G-T-G)-A--L-activated cells and (T-T-G-G)-A--L, whereas (T,G)-A--L could challenge the latter cells to mediate significant responses. Similar but not identical cross reactions were observed when primed spleen cells or lymph nodes were transferred to irradiated recipients that were boosted for the production of antibodies. In contrast to observations at the level of cellular responses, (T-G-T-G)-A--L-primed spleen or lymph node cells could not be boosted with (T,G)-A--L for the production of detectable amounts of antibodies, although boosting with the homologous antigen resulted in significant levels of (T-G-T-G)-A--L-specific antibodies. Transfer experiments in which mixtures of T and B cells, each primed to a different ordered polypeptide antigen, were injected into irradiated recipients showed that successful cooperation occurs provided that the boost is given with the T-cell-specific antigen. The antibodies produced were specific to the antigen used for B-cell priming. The T-cell-B-cell collaboration probably occurs through specific determinants that are shared between the two antigens in which the ordered peptides are attached to the same multichain polymer and that are recognized by both the T and the B cells.

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.

Antiviral response elicited by a completely synthetic antigen with built-in adjuvanticity

In a previous study we demonstrated that antiviral response against the coliphage MS-2 can be elicited by immunization with a synthetic antigen consisting of a conjugate (P2-A -- L) of a synthetic fragment (P2) of the virus coat protein attached to a synthetic polymeric carrier. The antiviral response was induced when the antigen was administered in complete Freund's adjuvant or when it was administered in incomplete adjuvant, provided that a peptidoglycan was covalently attached to it. In the present study we demonstrate the adjuvant effect of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) in this system. Immunization with a mixture of MDP and P2-A -- L brought about only slight enhancement in the titer of neutralizing antibodies, as compared to the immunization with P2-A -- L in saline. The best results were achieved when the MDP was chemically conjugated to P2-A -- L. This completely synthetic material, when administered in aqueous solution, yielded highly inactivating antiserum with a titer similar to that obtained with complete Freund's adjuvant in the absence of MDP. MDP-P2-A -- L elicited also a humoral immune response to MDP, but with much lower titer than that induced by complete Freund's adjuvant containing P2-A -- L only. It was also observed that the capacity of MDP-P2-A -- L to increase resistance against infection was more than a 100-fold greater than that of unconjugated MDP.

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 regulation of delayed-type hypersensitivity responses to poly(LTyr,LGu)-poly(DLAla)--poly(LLys). I. Expression of the genetic defect at two phases of the immune process

Delayed-type hypersensitivity (DTH) responses served in this study as an experimental model for the analysis of genetic regulations of T-cell responses. Educated irradiated cells from H-2b mice mediated responses in syngeneic recipients, whereas mice of the a, d, f, k, and s haplotypes were nonresponders to poly(LTyr,LGlu)-poly(DLAla)--poly(LLys)[(T,G)-A--L]. These results suggest that cell-mediated immune responsiveness to (T,G)-A--L is linked to the H-2 complex, as was shown for humoral responses. Educated irradiated T cells of F1 hybrids between high and low responders mediated DTH responses, which indicates that the gene(s) controlling the DTH responses is dominant. To analyze the genetic defect in DTH responses to (T,G)-A--L, we separated the T-cell activation phase from the effector phase that was determined in recipient mice. Two types of nonresponders were observed: (a) When lymphocytes of the a or k haplotypes were educated in a syngeneic environment and then transferred into hybrids between the parental (nonresponder x responder) F1 recipients, DTH responses could have been manifested. (b) On the other hand, no DTH responses could be mediated by transferring educated cells of the H-2s or H-2f origin into the appropriate F1 recipients. In addition, irradiated F1 cells that had been activated to (T,G)-A--L could not mediate DTH responses in both types of nonresponder recipients. These results suggest that T cells of H-2k or H-2a mice can be activated to generate DTH responses to (T,G)-A--L and that the defect in these mouse strains is expressed in another cell population needed for the manifestation of the DTH reaction in the recipient mice. In contrast, T cells of H-2s and H-2f origin cannot be activated to (T,G)-A--L and, thus, fail to manifest DTH responses.

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.

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

In previous publications it was shown by avidity measurements, cross-reactivity patterns and genetic analyses, that the tetrapeptide T-T-G-G is the immuno-dominant epitope of the synthetic polypeptide (T, G)-A--L. In the present study this close immunological relationship between the random multichain copolymer (T, G)-A--L and the ordered analogue (T-T-G-G)-A--L is extended by two additional criteria. First, the immune response against (T-T-G-G)-A--L in H-2k nonresponder mouse strains can be reconstituted to high antibody levels by complexing this antigen to methylated bovine serum albumin, as was tested earlier for (T,G)-A--L. The antibodies elicited upon reconstitution in both antigenic systems are directed mainly against the same determinant, T-T-G-G. Second, isoelectric focusing analysis of specific antisera developed with radiolabeled antigen revealed restricted 7 S IgG antibody populations in high responder and reconstituted high and low responder mice. The spectra were found to be of similar complexity in the (T,G)-A--L and in the (T-T-G-G)-A--L system. From these data it was concluded that the repertoires of specific B cells to T-T-G-G are very similar in high and low responder strains, and the defect in the H-2k low responder systems should be located at the level of T-B cell cooperation.

Two genes in the major histocompatibility complex control immune response

Sixty-four (57.6%) of 111 cancer patients with cerebrospinal fluid cytology positive for malignant cells had cranial computed tomographic (CT) scans within 2 weeks before or after a lumbar puncture. Twenty-two (34.3%) of the 64 had abnormal CT findings indicative of leptomeningeal metastasis: (1) sulcal-cisternal enhancement, (2) ependymal-subependymal enhancement, (3) widened irregular tentorial enhancement, or (4) communicating hydrocephalus. Thirteen (59.6%) of these 22 patients had associated parenchymal metastases. Recognition of leptomeningeal disease may alter the management of patients with parenchymal metastases. Communicating hydrocephalus in cancer patients should be considered to be related to leptomeningeal metastasis until proven otherwise.

H-2-linked genetic control of antibody response to soluble calf skin collagen in mice

An autosomal dominant immune response gene could be demonstrated in congenic resistant strains of mice which is linked to the H-2 locus and controls the antibody response to soluble calf collagen. High responsiveness was associated with the H-2 alleles, b and f, low responsiveness with the H-2 alleles, d, k, m and r. Studies with calf procollagen, which contains an additional carrier moiety, indicated that these genetic differences might be expressed at the level of T cells.

The possible role of i region determined cell surface molecules in the regulation of immune responses

An hypothetical model has been presented by which I region determined cell surface molecules (Ia antigens) mediate the collaboration between T cells and B cells leading to control of the humoral immune response. The model proposes an analogy between Ia antigens and the constant regions of Ig chains. The absolute requirements of this model are: a) On the B cell the Ia antigen is closely associated with the Fc receptor; b) On the T cell the Ia antigen is closely associated with the product of a linked variable region gene which functions as a specific T cell binding site; and c) The interaction between the T cell Ia molecule and its B cell counterpart leads to B cell activation. By the proposed interactive model no additional Ir gene products are required to explain current concepts of Ir gene function. The experimental evidence from our own laboratory and elsewhere upon which this model is based has been reviewed and a variety of consequences and predictions of the model have been examined. There are numerous aspects of the model which, because of a lack of hard data, are open to alternative explanations. The possible usefulness of this model should lie in its ability to suggest further experiments to elucidate the mechanism of B cell activation and control of the immune response.

I-region genes are expressed on T and B lymphocytes. Studies of the mixed lymphocyte reaction (MLR)

Unidirectional mixed lymphocyte reactions (MLR) were performed between mouse strains differing for various segments within the H-2 complex. Thymocytes and purified lymph node T cells and B cells were used as stimulator cells. In three of five combinations studied, differing only within the I region, both T and B cells stimulated in the MLR. This suggests that the region codes for both T- and B-cell surface structures. However, if the difference was restricted to one I subregion (I-C), only T cells stimulated. This finding suggests that some of the I-region genes may be expressed either in T or in B cells.

Evidence for identity or close association of the Fc receptor of B lymphocytes and alloantigens determined by the Ir region of the H-2 complex

Immunoglobulin complexes, composed of heat-aggregated human Ig, were shown to bind to mouse B lymphocytes of a variety of strains, but not to either thymocytes or thymus-derived (T) lymphocytes under a variety of conditions. It was shown that this binding was not due to either natural human antibodies against mouse nor to nonspecific binding of human Ig by mouse lymphocytes. Such complexes were shown to bind to the same sites which bind mouse antibody-antigen complexes. This site is known as the Fc receptor. The binding of Ig complexes to mouse B lymphocytes was markedly inhibited by pretreatment of the lymphocytes with anti-H-2 antisera. A series of experiments indicated the specificity of this result, including the fact that this inhibition was shown not to be due to the artifact of shedding of H-2 antibody-antigen complexes, nor to nonspecific steric inhibition. The antibodies within anti-H-2 antisera which were responsible for this inhibition were specific for alloantigens associated with the Ir region of the H-2 complex (Ia antigens). Antiserum specific for these Ia antigens produced inhibition, whereas antisera specific for antigens determined by the K or D regions of the H-2 complex did not. Evidence was obtained using F(1) hybrid cells that at least some Ia antigens of both parental types are expressed on every B lymphocyte (i.e. codominant expression). These data indicate that the Fc receptor and a series of alloantigens controlled by the Ir region of the H-2 complex are identical or closely associated on the B-lymphocyte surface membrane. This observation may have implications for the mechanism of control of the immune response.

Antibody response of inbred mouse strains to ordered tetrapeptides of tyrosine and glutamic acid attached to multichain polyalanine or polyproline. Tyr-Tyr-Glu-Glu is a major determinant of the random poly-(Tyr, Glu)-polyDLAla--polyLys

Five inbred mouse strains which represent high and low responders to the random synthetic polypeptide poly(LTyr,LGlu)-polyDLAla--polyLLys, designated (T, G)-A--L, to which the immune response is controlled by an H-2-linked gene, were immunized with three ordered tetrapeptides composed of tyrosine and glutamic acid attached either to multichain poly-DL-alanine or to polyproline. Only one of the three antigenic determinants, namely tyrosyl-tyrosyl-glytamyl-glutamic acid (T-T-G-G), resembled the random peptide (T, G) in the pattern of immune responses elicited against it, and in the cross-reactivity of the specific antibodies with (T, G)-A--L. The immune response pattern to the other two ordered tetrapeptides, T-G-T-G and G-T-T-G, was different from that obtained with (T, G)-A--L, and no cross-reactivity was detected between the antibodies provoked with these peptides and (T, G)-A--L. Thus, it is suggested that T-T-G-G is a major determinant in the random (T, G)-A--L.

Antigen-specific thymus cell factors in the genetic control of the immune response to poly-(tyrosyl, glutamyl)-poly-D, L-alanyl--poly-lysyl

The genetic control of the antibody response to a synthetic polypeptide antigen designated poly-L(Tyr, Glu)-poly-D,L-Ala--poly-L-Lys [(T, G)-A--L] has been studied in congenic high responder C3H.SW (H-2(b)) and low responder C3H/HeJ (H-2(k)) strains of mice. This response is controlled by the Ir-1 gene and is H-2 linked. The method employed was to study the ability of specifically primed or "educated" T cells of each strain to produce cooperative factors for (T, G)-A--L in vitro. Such factors have been shown to be capable of replacing the requirement for T cells in the thymus-dependent antibody response to (T, G)-A--L in vivo. The T-cell factors produced were tested for their ability to cooperate with B cells of either high or low responder origin by transfer together with bone marrow cells and (T, G)-A--L into heavily irradiated, syngeneic (for bone marrow donor) recipients. Direct anti-(T, G)-A--L plaque-forming cells were measured later in the spleens of the recipients. The results showed that (a) educated T cells of both high and low responder origin produced active cooperative factors to (T, G)-A--L, and no differences between the strains in respect to production of T-cell factors could be demonstrated; and (b) such factors, whether of high or low responder origin, cooperated efficiently with B cells of high responder origin only, and hardly at all with B cells of low responder origin. The conclusion was drawn that the cellular difference between the two strains lies in the responsiveness of their B cells to specific signals or stimuli received from T cells. As far as could be discerned by the methods used, no T-cell defect existed in low responder mice and the expression of the controlling Ir-1 gene was solely at the level of the B cells in this case.

The role of the thymus in a genetically controlled defect of the immune response at the carrier level

The genetic control of the immune response may be either specific for antigenic carrier or for determinant. We describe here results which show that a carrier-dependent strain defect in immune response is reflected in thymocytes. These results are in agreement with our hypothesis that the genetic defect in the immune response is reflected in thymocytes when the poor response is at the carrier level, whereas it is expressed in the bone marrow population when the low responsiveness is strictly at the determinant level. SWR mice are low responders to multichain polyproline. Furthermore, this mouse strain does not produce antibodies to determinants such as peptides of phenylalanine and glutamic acid (Phe,Glu) or to the loop peptide of lysozyme when attached to polyproline, although they respond well to the same antigenic determinants when conjugated to multichain poly(DL-alanine). Transfer experiments in which irradiated SWR recipients were injected with excess of DBA/1 thymocytes (which do not exhibit a defect in response to polyproline) mixed with graded numbers of SWR marrow cells, prior to immunization with poly(Tyr,Glu)-poly(Pro)--poly(Lys), have indicated that the poor response potential of SWR mice to polyproline is not reflected in their bone marrow cells. Allogeneic transfers in which mixtures of thymocytes and marrow cells from high and low responders were injected into irradiated mice, followed by immunization with poly(Tyr,Glu)-poly(Pro)--poly(Lys) or poly(Phe,Glu)-poly(Pro)--poly(Lys) have demonstrated a clear defect in the thymus derived population of SWR mice when the response potential to polyproline and to determinants attached to it was tested.