Production of anti-idiotypic antibodies by immunization with a pair of complementary peptides

Previous investigations have suggested that pairs of peptides specified by complementary RNA sequences (termed complementary peptides) can interact with one another. In the light of this finding, we hypothesized that an antibody directed against a peptide might interact with an antibody against its complementary peptide at the antigen combining site. To address this possibility, polyclonal antibodies against a peptide, Leu-Glu-Arg-Ile-Leu-Leu (LERILL), and its complementary peptide, Glu-Leu-Cys-Asp-Asp-Asp (ELCDDD), were made monospecific by affinity chromatography. Using radioimmunoassays, anti-ELCDDD antibodies were shown to interact with 125I-anti-LERILL antibodies but not with 125I-control antibodies. More importantly, the interaction of the two antibodies could be blocked using either peptide antigen, but not with control peptides. Furthermore, 125I-anti-LERILL binding to LERILL could be blocked with anti-ELCDDD antibody and vice versa. We concluded therefore that antibody/antibody binding occurred at or near the antigen combining site, demonstrating that this interaction was an idiotypic/anti-idiotypic one.

Monoclonal antibody against a peptide specified by [Met]-enkephalin complementary RNA recognizes the delta-class opioid receptor

Monoclonal antibodies (MAB) were developed which recognize a peptide, His-Glu-Ala-Pro-Ile (HEAPI), encoded by the RNA complementary to the mRNA specifying [Met]-enkephalin. One such MAB (designated 6193) exhibited a high degree of reactivity to the peptide sequence. Other characteristics of 6193 MAB include: the ability to block opioid ligand binding in a radioreceptor assay; agonist activity similar to opioid peptides in suppressing cAMP production; and the recognition of a 58 kDa protein on the surface of the neuroblastoma x glioma cell line, NG108-15. These results are consistent with a reactivity of 6193 MAB with the delta-class opioid receptor.

Complementary peptides as interactive sites for protein binding

The observation that pairs of peptides encoded from complementary strands of nucleic acids can bind one another suggested to us that proteins might use similar "complementary peptide" sequences to facilitate their interactions with other proteins or peptides. Here we review evidence to support this hypothesis. Investigations by us and by others showed that receptors and their ligands may use complementary peptide sequences or their analogs to facilitate binding. In addition, antibodies made against pairs of complementary peptides bind one another in an idiotypic/anti-idiotypic fashion. Taken together, these findings suggest that complementary peptide sequences may be used as recognition units by pairs of proteins which interact.

Individuals infected with HIV possess antibodies against IL-2

Studies are presented here which demonstrate that antibodies reacting with human interleukin-2 (IL-2) are present in the sera of patients infected with the human immunodeficiency virus (HIV). It is likely that these antibodies are present due to a homology between the HIV envelope protein and IL-2. The homologues are six amino acids in length corresponding to the carboxy terminus of gp41, Leu-Glu-Arg-Ile-Leu-Leu (LERILL), and residues 14-19 of secreted IL-2, Leu-Glu-His-Leu-Leu-Leu (LEHLLL). Thus, we questioned whether antibodies made against this HIV envelope peptide would cross-react with IL-2. Not only do a high percentage of the HIV-infected individuals tested here have antibodies against LERILL, but these antibodies cross-react with the IL-2 sequence, LEHLLL. Additional antigenic processing of IL-2 is suggested by the finding that epitopes other than this sixmer are also recognized by antibodies in patients' sera. Thus, these studies suggest a mechanism by which infection with HIV can induce a potentially suppressive autoimmune response. Specifically, antibodies against an HIV envelope peptide cross-react with an epitope in IL-2.

Production of immunoreactive growth hormone by mononuclear leukocytes

In the present study, we evaluated whether mononuclear leukocytes could synthesize and secrete growth hormone (GH) in vitro. By using RNA slot blot analysis, we detected maximum spontaneous levels of specific GH mRNA in the cytoplasm of rat leukocytes after a 4-h incubation. Northern gel analysis demonstrated that the specific leukocyte GH RNA was polyadenylated and had a molecular mass of 1.0 kb. Further studies using immunofluorescence, antibody affinity chromatography, and Sephacryl gel filtration indicate that leukocytes secrete a high molecular weight (greater than 300,000) and a low molecular weight (approximately 22,000) immunoreactive GH (irGH). A substantial amount of the high molecular weight irGH can be converted to the lower molecular weight form after reduction with mercaptoethanol. The irGH appeared to be de novo synthesized because it could be radiolabeled with tritiated amino acids and its production could be blocked by previous incubation of leukocytes with cycloheximide. The replication of Nb2 rat node lymphoma cells was stimulated by affinity-purified human lymphocyte-derived irGH. The growth stimulation was blocked by specific antibodies to hGH. We conclude that lymphocytes produce an irGH that is similar to if not identical to pituitary GH in terms of bioactivity, antigenicity, and molecular weight. The findings demonstrate a potential regulatory loop between the immune and neuroendocrine tissues.

Antibodies against a peptide sequence within the HIV envelope protein crossreacts with human interleukin-2

Recent investigations have identified a homologous sequence between the lymphokine interleukin 2 (IL-2) and the envelope protein of HIV. This homology is one of six amino acids corresponding to interleukin-2 (IL-2) residues 14-19 (Leu-Glu-His-Leu-Leu-Leu) and to the carboxy terminal six amino acids of HIV envelope protein gp41 (Leu-Glu-Arg-Ile-Leu-Leu). Thus, it is conceivable that an anti-HIV antibody response would generate antibodies which would crossreact with IL-2. We show here that the two peptides are recognized by the immune system as being almost identical. More importantly, antibodies against the HIV envelope peptide bind IL-2. Thus, these studies are the first step in investigating what could be characterized as an HIV-induced autoimmune response, that is, the induction of antibodies to the HIV envelope protein which also crossreact with IL-2.

Purification of an angiotensin II binding protein by using antibodies to a peptide encoded by angiotensin II complementary RNA

We have generated a monospecific antibody to a synthetic peptide encoded by an RNA complementary to the mRNA for angiotensin II (AII) and determined whether this antibody recognizes the AII receptor. We demonstrate that the antibody competes specifically with 125I-labeled AII for the same binding site on rat adrenal membranes. Furthermore, we show that this antibody inhibits the secretion of aldosterone from cultured rat adrenal cells, suggesting that the antibody recognizes the biologically relevant AII receptor. Finally, we demonstrate that antibody to the complementary peptide can be used to immunoaffinity-purify a protein of Mr 66,000 that specifically binds radiolabeled AII.

The production of antibodies which recognize opiate receptors on murine leukocytes

An antibody has been developed which recognizes opiate receptors on cells of the immune system. This antibody blocks specific binding of the radiolabeled opiate receptor ligand, 3H-dihydromorphine, to receptors on murine splenocytes. Additionally, the anti-receptor antibody competes with beta-endorphin, met-enkephalin, and naloxone for the same binding site on the leukocytes. Moreover, the anti-receptor antibody possesses agonist activity similar to beta-endorphin in suppressing cAMP production by lymphocytes. These results suggest the development of an antibody which recognizes classical opiate receptors on cells of the immune system.

Immunoaffinity-purified opiate receptor specifically binds the delta-class opiate receptor ligand, cis-(+)-3-methylfentanylisothiocyanate, SUPERFIT

Using an antibody generated against the opiate receptor on NG108-15 cells, we recently purified the putative receptor from this hybrid cell line. We herein report that the purified receptor complex specifically binds tritiated cis-(+)-3-methylfentanylisothiocyanate (SUPERFIT), with the predominant binding associated with a 58 kDa polypeptide chain. Consistent with these findings is the in situ labeling of a 58 kDa protein with [3H]SUPERFIT on NG108-15 cells.

Changes in the DNA of lymphocytes from pristane treated rats

The effects of pristane (2,6,10,14-tetramethylpentadecane) on the cellular DNA of lymphoid cells from Copenhagen rats were examined by flow cytometry. Significant reductions in the mean relative fluorescent intensities of propidium iodide (PI) stained lymphocytes from peripheral blood, spleen, thymus and lymph nodes were observed after a single intraperitoneal injection of pristane. The altered PI staining characteristics were observed as early as 4 days and reached a maximum decrease between 1-4 weeks (depending upon the lymphoid cells examined) post pristane treatment. The pristane-induced effects on peripheral blood lymphocytes were observed to be dose dependent, transient and reinducible by a subsequent exposure to pristane. Further analyses, using gas-liquid chromatography to detect pristane in the blood and lymphoid tissues of treated rats, indicated significant increases over normal amounts of pristane. Furthermore, correlations existed between the times of maximum decrease in the fluorescence of PI stained cells and the amounts of pristane detected within the respective lymphoid tissues. By contrast no changes in the PI staining characteristics of kidney cells were observed, even though appreciable amounts of pristane were detected in this organ. Diphenylamine analyses indicated no differences in the amounts of DNA in lymphoid cells from pristane treated and untreated rats. Furthermore, lymphocytes from pristane-treated rats did not exhibit decreased fluorescence when fixed at pH 10 rather than pH 7.4 prior to PI staining. Collectively these results suggest that pristane may preferentially induce qualitative rather than quantitative changes in the DNA of lymphocytes.

Presence of ACTH and its receptor on a B lymphocytic cell line: a possible autocrine function for a neuroendocrine hormone

A mouse B lymphocytic cell line, designated BCL1, was found to produce immunoreactive ACTH and to secrete this molecule into culture supernates. The BCL1-derived ACTH induced Y-1 adrenal cells to undergo a steroidogeneic response and was eluted from gel filtration columns at a molecular weight similar to that expected for pituitary-derived ACTH. Furthermore, ACTH receptors were detected on the surface of BCL1 cells using indirect immunofluorescence and 125I-ACTH binding studies. Scatchard analysis demonstrated the presence of high and low affinity binding sites with dissociation constants of 4.5 x 10(-12) M and 2.8 x 10(-9) M, respectively. The production of both ACTH and its receptor by this B lymphocyte cell line suggests that an autocrine mechanism might be important for the maintenance of the transformed phenotype.

Antibodies to the binding site of the receptor for luteinizing hormone-releasing hormone (LHRH): generation with a synthetic decapeptide encoded by an RNA complementary to LHRH mRNA

A molecular recognition code has been hypothesized to exist in which ligands and their binding sites are encoded on complementary segments of genomic DNA. We have tested this hypothesis by generating a rabbit antibody to a synthetic decapeptide (complementary peptide) encoded by an RNA complementary to the mRNA for luteinizing hormone-releasing hormone (LHRH) and determining whether this antibody recognizes the LHRH receptor. When the antibody was used for immunoperoxidase staining of enzymatically dispersed rat anterior pituitary cells, only those that contained and secreted luteinizing hormone (i.e., the gonadotropes) were recognized. This staining could be abolished by preincubation with the complementary peptide or with an LHRH agonist, suggesting that the antibody is specific to the complementary peptide and is directed at the binding site of the receptor. Further evidence that the antibody recognizes the LHRH receptor was obtained in immunoblot experiments on solubilized receptors from pituitary glands. Immunoperoxidase staining with the antibody revealed two bands at 60 kDa and 51 kDa, which are values similar to those previously obtained for the LHRH receptor in photoaffinity-labeling experiments. The staining of these bands was inhibited by preincubation with the complementary peptide or an LHRH agonist. The antibody as well as the complementary peptide to LHRH also suppressed LHRH-stimulated luteinizing hormone release in a quantitative reverse hemolytic plaque assay, presumably by binding to the LHRH receptor and by binding LHRH, respectively. These findings suggest that the synthetic decapeptide whose sequence is specified by the complementary RNA to LHRH mRNA is sufficiently similar to an LHRH binding site that the peptide not only binds LHRH but was also recognized by the immune system as such a site. These findings provide strong support for the hypothesis that recognition molecules are encoded by complementary segments of genomic DNA.

An antibody to a peptide specified by an RNA that is complementary to gamma-endorphin mRNA recognizes an opiate receptor

The putative delta-opiate receptor complex has been identified by a new approach which employed an antibody that is directed against a peptide which binds gamma-endorphin and is specified by RNA that is complementary to that of gamma-endorphin mRNA. This antibody competes with beta-endorphin and naloxone for binding sites on the surface of neuroblastoma X glioma NG108-15 hybrid cells. The opiate receptor complex has an apparent molecular weight of 210,000 and is composed of four noncovalently associated subunits with apparent molecular weights of 68,000, 58,000, 45,000 and 30,000.

The HTLV-III envelope protein contains a hexapeptide homologous to a region of interleukin-2 that binds to the interleukin-2 receptor

A region of human interleukin-2 (IL-2) which was predicted to be a contact point with its receptor was used to locate a homologous region in the envelope protein of human T-lymphotropic retrovirus (HTLV-III). This homologous six amino acid peptide from the carboxy (C)-terminus of the HTLV-III envelope protein was found to inhibit the biological activity of human IL-2 in a murine spleen cell proliferation assay. When conjugated to a carrier protein, this peptide inhibited the binding of radiolabelled IL-2 to its receptor. The biological activity of the peptide was antagonized by a six amino acid peptide fragment of the IL-2 receptor which was predicted to be the contact point on the receptor that corresponded to the binding region of IL-2. The HTLV-III peptide also inhibited the binding of radiolabelled IL-2 to polyclonal anti-IL-2 antiserum. These data support the previous assignment of contact points between IL-2 and its receptor. They also suggest two possible mechanisms of immunosuppression during acquired immunodeficiency syndrome (AIDS). One involves direct competition of the envelope protein or its fragments with IL-2 for binding to the IL-2 receptor. The other involves antibodies to the envelope protein which crossreact with and neutralize IL-2.

The role of the Peyer's patch in carcinogenesis. II. 3-Methylcholanthrene-induced lymphoid malignancies in rat Peyer's patches

To determine whether B or T lymphoid malignancies could be induced following the exposure of lymphoid cells within different lymphoid organs to a potential chemical carcinogen, 3-methylcholanthrene (3-MC) was directly injected into surgically exposed Peyer's patches (PP), mesenteric lymph nodes (MLN), axillary lymph nodes (ALN) or spleens (SP) of Copenhagen rats. A high incidence of lymphoproliferative disorders was observed within rats which received 3-MC injections into the PP, but not in MLN, ALN or SP injected groups of rats. In addition to the PP environment, the dose of 3-MC and exposure to pristane were important factors in the induction of T versus B cell disorders. Whereas the B cell diseases were observed in pristane-treated rats which also received PP injections of low doses (5 or 50 micrograms) of 3-MC, in animals receiving a higher dose (500 micrograms) a much higher incidence of T cell disorders was detected. The observed lymphoproliferative diseases were categorized as B lymphocytic leukemias, B lymphomas or thymic lymphomas on the basis of histological examination of the tissues, white blood cell numbers and differentials, and the morphological and phenotypic characteristics of cell isolates. Abnormal DNA staining characteristics, increased soft agar cloning frequencies and metastasis of the leukemia or tumor cells indicated that malignant cells were associated with the proliferative diseases. Collectively the data indicate that primary lymphoid malignancies of either B or T cell origins may be preferentially and reproducibly induced by localizing low or high doses respectively, of 3-MC within the PP of rats exposed to pristane. These results suggest that PP may have a possible role in the carcinogenesis of lymphocytes following the exposure to chemical carcinogens via the gastrointestinal tract.

The role of the Peyer's patch in carcinogenesis. I. The adsorption from the gut and retention of 3-methylcholanthrene by Peyer's patches

Radiotracer methods were used to determine the distribution of 3-methylcholanthrene (3-MC) within the lymphoid organs of rats following i.g. intubation, i.l. injection into the small intestine, i.v. injection or direct injection of the Peyer's patches with 3-[6-14C]methylcholanthrene (14C-MC). The data indicate that the gut-associated Peyer's patches and mesenteric lymph nodes were exposed to higher amounts of orally administered 14C-MC than any of the other lymphoid organs. Whereas the Peyer's patches exhibited the highest sp. act. for longer periods of time when low amounts of 14C-MC were administered, the sp. act. of the mesenteric lymph node were greater when rats were intubated with higher amounts of 14C-MC. Furthermore, the Peyer's patches were exposed to higher amounts of possible metabolites of 14C-MC. Injection of 14C-MC into the small intestinal lumen resulted in increased ratios of the Peyer's patch sp. act. to mesenteric lymph node sp. act., indicating that by-passing the stomach altered the distribution patterns. Data from rats injected i.v. with 14C-MC demonstrated that mesenteric lymph nodes but not Peyer's patches adsorbed and retained 14C-MC from the blood and indicated that the 14C-MC associated with Peyer's patches of i.g. treated rats was adsorbed from the gut rather than from the blood. Results obtained from rats which were exposed to 3-MC by directly injecting Peyer's patches with 14C-MC also indicated that the Peyer's patches were able to retain 3-MC once localized within this lymphoid organ, to metabolize the 3-MC and to possibly excrete the polycyclic aromatic hydrocarbon into the small intestine. Collectively the data indicate that Peyer's patches have an important role in the adsorption from the gut and subsequent retention of 3-MC and hence may be a likely target organ for lymphoid carcinogenesis following oral exposure to carcinogenic polycyclic aromatic hydrocarbons.

Binding of peptides that are specified by complementary RNAs

An interesting pattern in the genetic code was reported previously [Blalock & Smith (1984) Biochem. Biophys. Res. Commun. 121, 203-207]. In the 5'-to-3' direction, codons for hydrophilic and hydrophobic amino acids are generally complemented by codons for hydrophobic and hydrophilic amino acids respectively. The average tendency of codons for 'unchanged' (slightly hydrophilic) amino acids was to be complemented by codons for 'unchanged' amino acids. We now show that the same pattern results when the complementary codon is read in the 3'-to-5' direction. This pattern is further shown to result in the interaction of peptides specified by complementary RNAs regardless of whether the amino acids are assigned in the 5'-to-3' or the 3'-to-5' direction. Here we demonstrate that peptides specified by complementary RNAs bind to each other with specificity and high affinity.

Molecular characterization of a corticotropin (ACTH) receptor

We have used a new methodology to generate a monospecific antiserum to the corticotropin (ACTH) receptor on mouse Y-1 adrenal cells. Using immunoaffinity chromatography the ACTH receptor was purified, and the molecular structure and 125I-ACTH binding characteristics were determined. A molecular weight (Mr) of 225 000 was determined for the complete ACTH receptor as analyzed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. The receptor was composed of 4 subunits with Mr 83 000, 64 000, 52 000 and 22 000. The 83 and 52 kDa subunits were disulfide linked and non-covalently associated with the 64 and 22 kDa subunits. The ability to specifically bind 125I-ACTH was localized to the 83 kDa subunit. The purified receptor possessed binding affinities of 3.4 X 10(10) M-1 and 1.0 X 10(9) M-1 as determined by Scatchard analysis.

Neuroendocrine peptide hormones and their receptors in the immune system. Production, processing and action

Recent findings indicate that the immune and neuroendocrine systems interact and modulate one another functionally. The mechanism for this seems to be that the 2 systems share a set of receptors and ligands (hormones). Cells of the immune system are able to synthesize neuroendocrine peptide hormones which are biologically active and produced in physiologically significant quantities. Furthermore, leukocytes possess functional receptors for these same neuroendocrine hormones which will specifically modulate immune responses. The structural and functional evidence for these interactions is reviewed and discussed in the context of a bidirectional regulatory circuit between the immune and neuroendocrine systems.

Immune system dysfunction contributes to the aetiology of spontaneous hypertension

Spontaneously hypertensive rats (SHRs) have a depressed T lymphocyte system, especially a reduced activity of the suppressor T cells, and it has been postulated that an auto-immune defect may be important in the aetiology of hypertension in these rats. In an earlier study we demonstrated that chronic immunosuppressive therapy prevents approximately 50% of the hypertension in the SHR. In the present study, an attempt was made to correct the immune imbalance by implanting thymic tissue from normotensive rats into SHRs. Weekly thymic implants from Wistar donor rats into 16-week-old SHRs produced a maximal reduction (P less than 0.05) in the tail-cuff pressure, after 4 weeks, to a level of 156 +/- 2.3 mmHg (n = 8) in thymus-implanted SHRs versus 189 +/- 2.5 mmHg (n = 6) in sham-implanted SHRs. Also, neonatal thymic implants delayed development of spontaneous hypertension and attenuated the final hypertensive state. Mean arterial pressure averaged 186 +/- 2.8 mmHg in 22-week-old, neonatally sham-implanted SHRs, while it was reduced (P less than 0.05) to 164 +/- 4.2 mmHg in the neonatally thymus-implanted SHRs at this time. The thymic implants had little effect on total T cell, helper T cell or suppressor T cell counts. However, the antihypertensive effect of the thymic implants was associated with a substantial increase in the blastogenic responsiveness of suppressor T cells from the SHRs. These results support the hypothesis that immunological dysfunction plays an important role in the aetiology of spontaneous hypertension.