Characterization of antisera to the naloxone-insensitive receptor for beta-endorphin on U937 cells generated by using the complementary peptide strategy

Antisera to the naloxone-insensitive receptor for beta-endorphin expressed on the U937 cell line were generated by using the complementary peptide strategy. A nanopeptide complementary to a C-terminal fragment of human beta-endorphin was synthesized as predicted by reading the beta-endorphin antisense mRNA 3' to 5'. By using enzyme-linked immunosorbent assay, rabbit antisera specific for the peptide complementary to beta-endorphin (C'-peptide) were characterized. With the exception of C'-peptide, preabsorption of the antisera with human-beta-endorphin1-31 or 10 unrelated peptides of 5 to 21 amino acids failed to reduce the enzyme-linked immunosorbent assay titer. Sucrose gradient separation was also used to show that the antisera failed to recognize beta-[125I]endorphin. Immunoglobulin to C'-peptide (10-800 micrograms/tube) inhibited the binding of beta-[125I]endorphin (1-2 nM) to intact U937 cells in a dose-dependent manner, whereas control immunoglobulin was ineffective. Moreover, immunoglobulin to C'-peptide failed to reduce [3H]naloxone binding to rat brain membrane. After binding and cross-linking of beta-[125I]endorphin to U937 cell membrane in the presence of beta-endorphin (2.5 x 10(-5) M), control immunoglobulin or anti-C'-peptide immunoglobulin, sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that anti-C'-peptide immunoglobulin inhibited binding to 44 and 59 kDa bands. Nonspecific antibody was completely ineffective, whereas beta-endorphin completely inhibited binding to the 44 kDa and partially to the 59 kDa band. Western blot analysis of U937 cell membrane showed bands at 64, 58 and 56 kDa. In summary, antibodies selective for C'-peptide displaced beta-endorphin from the naloxone-insensitive receptor on U937 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms of pathogenesis in scleroderma. I. Overproduction of interleukin 6 by fibroblasts cultured from affected skin sites of patients with scleroderma

Fibroblasts were cultured from affected skin sites of patients with progressive systemic sclerosis (PSS), from unaffected skin sites of the same patients, and from a healthy donor. The concentration of interleukin 6 (IL-6) in culture medium conditioned by the growth of early passage cells was determined by radioimmunoassay and by quantitative bioassay. Results demonstrated that fibroblasts from affected PSS skin produce from 6 to 30-fold higher levels of biologically active IL-6 compared to unaffected and control cells. In contrast, serum IL-6 concentrations in 6 of 8 patients examined were not significantly different from healthy donors. Serum IL-6 levels were elevated 2 to 3-fold in 2 of 8 patients examined. Thus, the overproduction of IL-6 by affected scleroderma fibroblasts does not necessarily correlate with a systemic increase in IL-6, but may increase its concentration locally. In view of its biological activities, including stimulation of antibody production and T cell activation, the overproduction of IL-6 by PSS fibroblasts in the lesions may play a significant role in the pathogenesis of PSS and may profoundly influence the course of the disease.

Human recombinant interleukin-4 induces proliferation and interleukin-6 production by cultured human skin fibroblasts

The effect of human recombinant interleukin-4 (hrIL-4) on normal human adult dermal fibroblasts in terms of proliferation and IL-6 production was studied. Fibroblasts were exposed to different concentrations of IL-4 for various periods of time. Proliferation was measured using a [3H]thymidine incorporation assay. IL-6 production was measured at the transcriptional, protein, and functional levels by Northern blot analysis, radioimmunoassay, and B9 bioassay, respectively. Our results show that hrIL-4 significantly stimulated (two- to fivefold) fibroblasts to increase the incorporation of [3H]thymidine in a dose- and time-dependent manner. However, hrIL-1, hrIL-2, hrIL-5, or hrTNF alpha, at the same concentration (100 U/ml) and for the same time period (4 days), did not. In addition, IL-4 significantly induced (four- to eightfold) the production of immunoreactive and biologically functional IL-6. However, IL-4 was not as potent an inducer of IL-6 as IL-1. The IL-4-induced IL-6 production was dose and time dependent and was due, at least in part, to a dramatic increase in the steady-state levels of IL-6 mRNA. This is the first report describing the ability of IL-4 to activate human dermal fibroblasts in terms of proliferation and IL-6 production.

The cytokine-like action of substance P upon B cell differentiation

B cells respond to a variety of effector molecules that can induce these cells to differentiate. One such molecule is the neuropeptide, substance P (SP). Previous studies have demonstrated the presence of SP receptors on lymphocytes while limited studies have been able to demonstrate the biological significance of their expression. SP has been shown to enhance IgA and IgM responses by Peyer's patch and splenic B cells. A limitation of these studies was that the direct effect of SP upon B cells was not ascertained, suggesting these B cells were stimulated via alternate mechanisms. To this end, evidence here will be discussed that SP can directly interact with clonal B lymphoma cells and highly purified splenic B cells. The data implicate SP as a late-acting B cell differentiation factor that requires an additional triggering mechanism to initiate the B cell differentiation process.

Modulation of the mRNAs encoding substance P and its receptor in rat macrophages by LPS

Numerous soluble factors and their receptors contribute to the regulation of immune responses. An important area of investigation concerns defining the regulation of expression of such receptor/ligand pairs, since understanding such events are central in the quest to manipulate immune responses. Receptors for the neuropeptide, substance P, are present on a variety of leukocytes, and these receptor positive cells respond to in vitro stimulation with substance P in a variety of ways. Unfortunately, little is known about the regulation of expression of substance P or its receptor in leukocytes. Here we begin to address this question by examining the ability of macrophages to express mRNAs which encode substance P and its receptor. A radiolabeled oligonucleotide probe complementary to the mRNA which encodes substance P (i.e., preprotachykinin mRNA) hybridized to a 1.3 kb RNA species present in rat macrophages. In addition, the expression of this RNA could be upregulated 6 to 8 fold when macrophages were stimulated with LPS. The ability of macrophages to synthesize and secrete immunoreactive-substance P was demonstrated by incorporation of L-[35S]methionine into material from macrophage cultures which could be recognized by a monoclonal antisubstance antibody. Macrophage RNA of approximately 3.1 kb in size was capable of hybridizing with an oligonucleotide probe complementary to rat brain substance P receptors. In addition, this RNA could be upregulated when cells were exposed to LPS. Taken together, these studies suggest that the genes used by neuronal cells and macrophages to encode substance P and its receptor are similar if not identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Substance P: a late-acting B lymphocyte differentiation cofactor

The peptide substance P has been recognized for years as having dramatic effects on such diverse physiological responses as blood pressure regulation, peristalsis of the gut, and salivation. More recently, demonstration of substance P receptors on leukocytes and modulation of leukocyte functions by this peptide suggested that it might also have a role in immune regulation. This review focuses on the growing body of evidence that demonstrates substance P-induced effects on one population of leukocytes, namely B lymphocytes. Despite the diversity of experimental techniques used, there is surprisingly good agreement as to the role substance P has in modulating B lymphocyte responses. In vivo treatments of rodents, which increase substance P concentrations in the periphery, increase the number of immunoglobulin-secreting cells in these animals. Conversely, infusion of substance P antagonists or depletion of substance P-containing neurons in rodents substantially reduces the animals' ability to synthesize immunoglobulins. With the use of cultures of B lymphocytes it was possible to demonstrate similar results. In the presence of polyclonal B cell activators, substance P augmented immunoglobulin secretion in cultures of purified B lymphocytes or B cell clones. The absence of accessory cells in these cultures suggested that substance P could act directly on activated B lymphocytes, and in fact these B cells were shown to express specific receptors for this peptide. It appears that the substance P receptors expressed by leukocytes are similar or identical to those expressed by neurons as evidenced by radioreceptor binding assays and detection of the gene encoding the substance P receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneously hypertensive rat: lymphoid depression is age dependent and mediated via a mononuclear cell subpopulation

Immune dysfunction has been reported in spontaneously hypertensive rats (SHR), particularly in mature animals with established hypertension. The current study examined the time course of development of immune dysfunction and defined its cellular basis in male SHR and control normotensive Wistar-Kyoto rats (WKY). Mitogen-induced proliferative responses in lymphoid cells obtained from induced proliferative responses in lymphoid cells obtained from SHR thymus and spleen before (age 4 wk) and during the development of (ages 8 and 12 wk) hypertension and in age-matched normotensive WKY were monitored. A 50% reduction in concanavalin A (Con A)-induced proliferative responses was seen in SHR thymocytes compared with those of WKY at 12 wk only, suggesting differences in immature T-cell populations. Con A-induced T-cell proliferative responses in splenocytes also differed between strains: greatest (as much as 8-fold) decreases were found in 12-wk-old SHR. Similar findings were obtained in splenocytes stimulated with lipopolysaccharide (LPS), indicating differences in B-cell function. Mononuclear cells depleted of their adherent cell population were prepared from SHR and WKY at 12+ wk of age and assayed for their proliferative responses to LPS and Con A. The remaining nonadherent mononuclear cells of SHR had proliferative responses equal to or greater than those of WKY. Further, when SHR splenic mononuclear cells were allowed to adhere to plastic, and the adherent fraction was co-cultured with either SHR G-10 nonadherent or unfractionated SHR splenic mononuclear cells, proliferative responses were suppressed by as much as 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroimmune modulation of lymphocyte function--I. Substance P enhances immunoglobulin synthesis in lipopolysaccharide activated murine splenic B cell cultures

Murine B cells have been shown to possess substance P (SP) receptors, but their functional and biological significance remains unresolved. While previous studies have suggested that SP can induce B cells to secrete Ig, the effect could be indirect since mixed cultures were used. In order to assess directly the ability of SP to trigger normal B cells, we have studied the effects of this neuropeptide on purified splenic B cells in vitro. Although an activation, e.g. lipopolysaccharide (LPS), was required, the functionality of the B cell SP receptors was clearly shown by the ability of subnanomolar concentrations of this neuropeptide to augment antibody secretion in a dose-dependent fashion. Specifically, IgM and IgG levels, determined by an isotype-specific sandwich ELISA, were greatly enhanced at 10(-10) M SP by as much as 500 and 572% respectively, while IgA levels were only modestly affected. Even picomolar concentrations of SP could significantly increase IgM levels. This observed enhancement of Ig production was SP specific since B cells co-cultured in the presence of excess SP antagonist were reduced to basal LPS-stimulated Ig levels. Furthermore, this synergistic stimulation by SP and LPS upon normal B cells could not be attributed to SP-induced cell proliferation since stimulatory concentrations of SP were not mitogenic and at high concentrations could inhibit cell proliferation. Rather, it was observed that the increased IgM and IgG secretion was in part attributable to a greater number of B cells secreting antibodies as demonstrated with an ELISPOT assay.(ABSTRACT TRUNCATED AT 250 WORDS)

The regulation of antibody responses by mini-cytokines

The presence of adrenocorticotropic hormone (ACTH) and substance P (SP) receptors on leukocytes is suggestive that these cells can respond to these ligands. To address this possibility, we have investigated the consequences of ACTH and SP stimulation of B cells. As a result, enhanced immunoglobulin synthesis mimicking an IL-4-like mechanism was noted. Importantly, this stimulation could be induced at ligand concentrations at or near the kD for their receptors. Herein these effects by ACTH and SP were described using B cell lymphoma cell lines and normal B cells.

A monoclonal anti-peptide antibody mimics adrenocorticotropic hormone activity

A monoclonal antibody that specifically recognizes the adrenocorticotropic receptor (ACTH) on rat adrenal cells was tested for hormonal activity. The antibody behaved as an agonist based on three different biological activities associated with ACTH. An antibody concentration of 16 micrograms/ml stimulated isolated rat adrenal cells to secrete 800 ng/10(4) cells of corticosterone with a concomitant 10-fold increase of cAMP to 30 pmol/10(5) cells. Antibody concentrations above 16 micrograms/ml inhibited mitotic activity in mouse Y-1 adrenal cells. A radio-immunoassay using an anti-ACTH antibody showed that the monoclonal anti-adrenocorticotropic receptor antibody and ACTH are antigenically related. These findings suggest that the anti-receptor antibody recognizes the ligand binding domain of the ACTH receptor.

Substance P acts directly upon cloned B lymphoma cells to enhance IgA and IgM production

The IgA producing murine B lymphoma, CH12.LX.C4.4F10 (4F10) and the IgM producing murine lymphoma, CH12.LX.C4.5F5 (5F5) were found to express substantial numbers of substance P (SP) receptors having dissociation constants equal to 0.69 nM. Binding of SP by these B lymphoma cells was via the tachykinin-specific C-terminus sequence, Phe-X-Gly-Leu-Met-NH2, because SP, SP antagonist (D-Pro2-D-Phe7-D-Trp9-SP), eledoisin, and substance K could effectively inhibit radiolabeled SP binding, whereas the SP N-terminus fragment, SP (1-4), could not. The functionality of these receptors could be demonstrated by the ability of subnanomolar concentrations of SP to induce Ig secretion in a dose-dependent fashion. However, the presence of a second stimulus in these cultures was required to obtain maximal increases. IgA secretion by 4F10 cells was elevated only 25 to 37%, and IgM secretion by 5F5 cells was not significantly increased in cultures in which nanomolar concentrations of SP were present. Conversely, coculturing 5F5 cells with a suboptimal concentration of LPS (50 ng/ml) and 10(-10)M SP resulted in an approximate threefold increase in supernatant IgM when compared to control cultures stimulated with LPS alone. While not as dramatic, 10(-10) M SP also enhanced IgA secretion of LPS-stimulated 4F10 cells by approximately 45%. This enhancement of Ig secretion was SP-specific, as evidenced by the ability of 1000-fold excess of SP antagonist to block SP-induced, but not LPS-induced, Ig production. Clearly, SP could act synergistically with LPS to enhance Ig secretion; therefore, we questioned whether this augmentation was also reflected at the level of H chain mRNA expression. 10(-9)M SP induced modest increases (50 to 60%) in mu-chain mRNA expression by LPS-stimulated 5F5 cells when compared with cells stimulated with LPS alone. The 4F10 cells did not display this magnitude of difference for alpha-chain mRNA expression. Thus, although SP-induced increases of mu-chain mRNA by 5F5 cells may contribute to the increased Ig secretion observed by these LPS-activated lymphocytes, it is unlikely that increased mRNA expression can totally account for the threefold increases in secretion that were observed.

Substance P acts directly upon cloned B lymphoma cells to enhance IgA and IgM production

The IgA producing murine B lymphoma, CH12.LX.C4.4F10 (4F10) and the IgM producing murine lymphoma, CH12.LX.C4.5F5 (5F5) were found to express substantial numbers of substance P (SP) receptors having dissociation constants equal to 0.69 nM. Binding of SP by these B lymphoma cells was via the tachykinin-specific C-terminus sequence, Phe-X-Gly-Leu-Met-NH2, because SP, SP antagonist (D-Pro2-D-Phe7-D-Trp9-SP), eledoisin, and substance K could effectively inhibit radiolabeled SP binding, whereas the SP N-terminus fragment, SP (1-4), could not. The functionality of these receptors could be demonstrated by the ability of subnanomolar concentrations of SP to induce Ig secretion in a dose-dependent fashion. However, the presence of a second stimulus in these cultures was required to obtain maximal increases. IgA secretion by 4F10 cells was elevated only 25 to 37%, and IgM secretion by 5F5 cells was not significantly increased in cultures in which nanomolar concentrations of SP were present. Conversely, coculturing 5F5 cells with a suboptimal concentration of LPS (50 ng/ml) and 10(-10)M SP resulted in an approximate threefold increase in supernatant IgM when compared to control cultures stimulated with LPS alone. While not as dramatic, 10(-10) M SP also enhanced IgA secretion of LPS-stimulated 4F10 cells by approximately 45%. This enhancement of Ig secretion was SP-specific, as evidenced by the ability of 1000-fold excess of SP antagonist to block SP-induced, but not LPS-induced, Ig production. Clearly, SP could act synergistically with LPS to enhance Ig secretion; therefore, we questioned whether this augmentation was also reflected at the level of H chain mRNA expression. 10(-9)M SP induced modest increases (50 to 60%) in mu-chain mRNA expression by LPS-stimulated 5F5 cells when compared with cells stimulated with LPS alone. The 4F10 cells did not display this magnitude of difference for alpha-chain mRNA expression. Thus, although SP-induced increases of mu-chain mRNA by 5F5 cells may contribute to the increased Ig secretion observed by these LPS-activated lymphocytes, it is unlikely that increased mRNA expression can totally account for the threefold increases in secretion that were observed.

Modulation of IgM secretion and H chain mRNA expression in CH12.LX.C4.5F5 B cells by adrenocorticotropic hormone

The murine B cell line CH12.LX.C4.5F5 (CH12 (5F5) expresses adrenocorticotropin (ACTH) receptors, which can modulate IgM secretion by these cells. Interestingly, the response to ACTH was concentration dependent, inducing IgM secretion at subnanomolar amounts and suppressing secretion at micromolar amounts. With the use of an enzyme-linking immunospot assay it was possible to demonstrate that the ACTH-induced increase in IgM secretion by CH12 (5F5) cells was caused at least in part by an increase in the number of cells secreting IgM. CH12 (5F5) cells activated with suboptimal concentrations of LPS demonstrated a similar biphasic response. ACTH at concentrations of 10(-13) to 10(-9) M augmented IgM secretion in LPS-activated cells as much as sixfold, whereas 10(-6) M ACTH slightly decreased LPS-induced IgM secretion. At the mRNA level, subnanomolar concentrations of ACTH increased microH chain mRNA expression up to twofold in unstimulated or LPS-stimulated CH12 (5F5) cells. Taken together, these studies show that physiologically relevant concentrations of ACTH can interact directly with receptors on these B lymphocytes to enhance IgM secretion and microH chain mRNA expression. Although ACTH does increase intracellular cAMP levels in CH12 (5F5) B cells, it is unlikely that the induction of this second messenger pathway is by itself responsible for the ACTH induced B cell differentiation. The concentration of ACTH necessary to stimulate significant intracellular cAMP increases was 10- to 100-fold higher than that required to increase IgM secretion. Furthermore, CH12 (5F5) cells treated with varying concentrations of 8-bromo cAMP or cholera toxin were inhibited in their ability to secrete IgM. These results strongly suggest that the enhancing effects of ACTH on CH12 (5F5) IgM secretion are via mechanisms independent of those mediated by cAMP.

Modulation of IgM secretion and H chain mRNA expression in CH12.LX.C4.5F5 B cells by adrenocorticotropic hormone

The murine B cell line CH12.LX.C4.5F5 (CH12 (5F5) expresses adrenocorticotropin (ACTH) receptors, which can modulate IgM secretion by these cells. Interestingly, the response to ACTH was concentration dependent, inducing IgM secretion at subnanomolar amounts and suppressing secretion at micromolar amounts. With the use of an enzyme-linking immunospot assay it was possible to demonstrate that the ACTH-induced increase in IgM secretion by CH12 (5F5) cells was caused at least in part by an increase in the number of cells secreting IgM. CH12 (5F5) cells activated with suboptimal concentrations of LPS demonstrated a similar biphasic response. ACTH at concentrations of 10(-13) to 10(-9) M augmented IgM secretion in LPS-activated cells as much as sixfold, whereas 10(-6) M ACTH slightly decreased LPS-induced IgM secretion. At the mRNA level, subnanomolar concentrations of ACTH increased microH chain mRNA expression up to twofold in unstimulated or LPS-stimulated CH12 (5F5) cells. Taken together, these studies show that physiologically relevant concentrations of ACTH can interact directly with receptors on these B lymphocytes to enhance IgM secretion and microH chain mRNA expression. Although ACTH does increase intracellular cAMP levels in CH12 (5F5) B cells, it is unlikely that the induction of this second messenger pathway is by itself responsible for the ACTH induced B cell differentiation. The concentration of ACTH necessary to stimulate significant intracellular cAMP increases was 10- to 100-fold higher than that required to increase IgM secretion. Furthermore, CH12 (5F5) cells treated with varying concentrations of 8-bromo cAMP or cholera toxin were inhibited in their ability to secrete IgM. These results strongly suggest that the enhancing effects of ACTH on CH12 (5F5) IgM secretion are via mechanisms independent of those mediated by cAMP.

Interleukin-2 does not attenuate hypertension in spontaneously hypertensive rats

It was recently reported that interleukin-2, when administered as a single bolus injection (5,000 units/kg), could prevent the development of hypertension in young spontaneously hypertensive rats and lower blood pressure to normotensive levels in spontaneously hypertensive rats with established hypertension. Consequently, efforts were made to duplicate this finding. Male spontaneously hypertensive rats (35 days old) were injected subcutaneously with 50,000 units/kg (3,500 units/rat) of recombinant interleukin-2 (Amgen) and had systolic blood pressure measured twice weekly by the tail-cuff technique. Systolic blood pressure in the interleukin-2-treated group was not significantly different from the vehicle-treated control group at any time point over 32 days of follow-up. A second injection of recombinant interleukin-2 (5,000 units/kg) was administered 32 days after the first injection. Again, no reduction in blood pressure was observed in the interleukin-2-treated group over an additional 38 days. Mean arterial pressure (+/- SEM) measured via intra-arterial cannula in conscious rats at age 105 days (38 days after the second treatment) was 168.5 +/- 3.5 mm Hg in interleukin-2-treated spontaneously hypertensive rats and 170.3 +/- 3.6 mm Hg in vehicle-treated controls. Both recombinant interleukin-2 preparations conformed to their respective manufacturer's indicated specific activity as determined by the ability of the interleukin-2 to induce proliferation of the interleukin-2-dependent cell line HT-2. Thus, this study demonstrated that interleukin-2 was ineffective in preventing or attenuating hypertension in spontaneously hypertensive rats.

5'-3' and 3'-5' translation of the same RNA results in hydropathically similar peptides that are antigenically related

When a single RNA sequence is read in either the 5'-3' or 3'-5 direction, the translated peptides often are hydropathically similar even though their sequences may be different. To investigate whether hydropathically similar peptides might also be antigenically related, two peptides were synthesized from the substance P anti-sense RNA transcript: CAU CAA UCC AAA GAA CUG CUG AGG CUU GGG UCG. Translation of this RNA in the 5'-3' direction and in the 3'-5' direction resulted in two different peptides. HQSKELLRLGS and AGFGVVKKPNY, respectively. As anticipated, both peptides shared similar hydropathic profiles but were quite different with respect to their sequences. To examine their antigenic relatedness, mice were immunized with either peptide, and monoclonal antibodies were produced. Using an enzyme-linked immunosorbent assay, it was possible to demonstrate that the majority of monoclonal antibodies, selected for reactivity against the original immunogen, also reacted with the other peptide. The observed binding was determined to be specific since reactivity could be blocked with either soluble peptide. Thus, we demonstrate that hydropathically similar peptides obtained from the same RNA but translated in opposite directions are antigenically related despite difference in amino acid sequences.

Substance P production by P388D1 macrophages: a possible autocrine function for this neuropeptide

This study investigates the ability of P388D1 macrophages to synthesize and secrete substance P (SP). Using a monoclonal anti-SP antibody (termed MASP-1) coupled to Sepharose, it was possible to immunoaffinity purify from culture supernates a peptide that was antigenically related to SP. P388D1 macrophage cultured in the presence of 35S-methionine secreted into culture supernates a labelled peptide which could be recognized by MASP-1. Affinity-purified, P388D1-derived SP was shown to be chemically similar to synthetic SP using gel-filtration chromatography and reverse-phase HPLC. In addition, an RIA using a polyclonal, monospecific antibody was used to quantify the amount of secreted SP in cultured supernates. P388D1 macrophages secreted 222 pg SP per 10(8) cells, whereas SP secretion by control thymocyte cultures was not detectable. The functionality of the P388D1-derived SP was also investigated. Since exogenously added SP can increase secretion of an interleukin-1 (IL-1)-like activity in these cells, we questioned whether an anti-SP antibody could remove P388D1-secreted SP from the culture, and in turn reduce cytokine production. By culturing varying dilutions of MASP-1 with P388D1 cells, it was possible to decrease cytokine production by P388D1 cells compared to cultures containing no antibody or with normal mouse immunoglobulin G (IgG). Taken together, these studies demonstrate that macrophage-derived SP may function in an autocrine or paracrine fashion to modulate macrophage function.

A monoclonal anti-peptide antibody recognizes the adrenocorticotropic receptor

We have produced a monoclonal antibody that specifically recognizes the adrenocorticotropic receptor on rat adrenal cells. The immunogen was designed from an RNA sequence complementary to the mRNA coding for ACTH1-24. This complementary peptide, termed HTCA, has been shown to specifically bind ACTH and was proposed to mimic the ACTH binding site of the hormone receptor. The monoclonal anti-HTCA antibody recognized a restricted domain of the HTCA peptide, bound to Y-1 adrenal cells with a KD of 1.8 nM, and blocked the binding of 125I-ACTH to rat adrenal cells. These findings show that anti-HTCA competes with ACTH for binding to the ACTH receptor.

Anti-opioid receptor antibody recognition of a binding site on brain and leukocyte opioid receptors

Opioid receptors reportedly exist on neuronal tissue of central and peripheral origin as well as on cells of the immune system. Previously, an opioid receptor has been purified from the neuroblastoma x glioma hybrid cell line, NG108-15 cells. In an effort to compare these results with opioid receptors isolated from primary neuronal tissue, we employed a methodology based on the molecular recognition theory to develop a monoclonal antibody which was used to isolate and biochemically characterize murine brain opioid receptors. We herein report the purification of an opioid receptor from mouse brain with a molecular weight of 65,000 daltons (range was 62-70 kD under reducing conditions) using a monoclonal antibody to an (the) opioid receptor. In situ labeling experiments with the delta-class selective opioid receptor affinity ligand, cis-(+)-3-methylfentanylisothiocyanate (SUPERFIT) of brain membrane confirmed these observations. Moreover, SUPERFIT, when coupled to the binding site, could block the recognition of the receptor by the monoclonal antibody. However, the selective, mu-class opioid receptor affinity reagent, 2-(p-ethoxybenzyl)-1-N,N-diethylaminoethyl-5-isothiocyanatobenz imidazole was ineffective at masking the binding site from recognition by the monoclonal antibody. Likewise, opioid-like receptors were purified from murine leukocytes which migrated at a molecular weight of 58,000 daltons under nonreducing conditions and 70,000 daltons under reducing conditions. In addition, immunoaffinity-purified receptor is shown to specifically bind the delta-class-selective opioid ligand, cis-(+)-3-methylfentanylisothiocyanate as well as the endogenous opioid peptides, beta-endorphin and [Met]-enkephalin.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation, purification, and partial characterization of suppressin, a novel inhibitor of cell proliferation

Pituitary tissues were investigated for the presence of regulatory molecules that would alter the function of lymphoid cells. A novel endogenous polypeptide inhibitor of basal and mitogen-stimulated splenocyte DNA synthesis and proliferation, suppressin, was isolated from bovine pituitary glands. Suppressin is a potent inhibitor of basal and mitogen-stimulated splenocyte proliferation at picomole and nanomole concentrations with 50% inhibition occurring 2.8 x 10(-9) M. Suppressin was purified to apparent homogeneity using sequential (NH4)2SO4 precipitation, ion-exchange chromatography, and preparative native gel electrophoresis. Biochemical characterizations of suppressin showed that this inhibitory molecule was a monomeric polypeptide with (i) a Mr = 63,000 and (ii) a pI of 8.1. Finally, metabolic labeling studies using a rat pituitary tumor cell line, GH3, showed that suppressin was synthesized de novo and secreted by these cells.

Antipeptide antibodies that recognize a lymphocyte substance P receptor

In an effort to investigate the presence of substance P (SP) receptors on lymphocytes, polyclonal antibodies against SP receptors were developed. The immunogen used to generate these antibodies was a peptide encoded by an RNA complementary to the mRNA for SP. The rationale for using this SP complementary peptide (termed SP CP) as an immunogen resulted from the observation that 3H-SP bound to microtiter wells coated with SP CP in a dose dependent and saturable fashion. Furthermore, binding was blocked with excess unlabeled SP or SP antagonist, D-Pro2-D-Phe7-D-Trp9-SP. Inasmuch as the peptide, SP CP, specifically bound 3H-SP, we hypothesized that antibodies against this peptide might recognize a SP receptor binding site. Using the SP receptor positive lymphoblast cell line, IM-9, affinity-purified antibodies against SP CP but not antibodies against keyhole limpet hemocyanin recognized a molecule on the surface of IM-9 cells. Anti-SP CP binding to IM-9 cells was blocked with excess SP antagonist, suggesting that the antibody and the SP antagonist were competing for the same binding site. In support of this possibility, anti-SP CP antibodies blocked 3H-SP binding to IM-9 cells. An immunoaffinity column coupled with antibodies against SP CP bound protein from solubilized IM-9 cells. This isolated protein bound 125I-Tyr8-SP and binding was specifically blocked with SP as well as by SP antagonist, neurokinin A, and eledoisin. Passthrough material did not bind SP suggesting that a SP receptor had been purified. Western blot analysis of solubilized IM-9 cell proteins using anti-SP CP antibodies but not preimmune IgG recognized a single protein of 58,000 D. Taken together, these results demonstrate that antibodies against SP CP recognize a SP receptor present on the lymphocyte cell line, IM-9.

Antipeptide antibodies that recognize a lymphocyte substance P receptor

In an effort to investigate the presence of substance P (SP) receptors on lymphocytes, polyclonal antibodies against SP receptors were developed. The immunogen used to generate these antibodies was a peptide encoded by an RNA complementary to the mRNA for SP. The rationale for using this SP complementary peptide (termed SP CP) as an immunogen resulted from the observation that 3H-SP bound to microtiter wells coated with SP CP in a dose dependent and saturable fashion. Furthermore, binding was blocked with excess unlabeled SP or SP antagonist, D-Pro2-D-Phe7-D-Trp9-SP. Inasmuch as the peptide, SP CP, specifically bound 3H-SP, we hypothesized that antibodies against this peptide might recognize a SP receptor binding site. Using the SP receptor positive lymphoblast cell line, IM-9, affinity-purified antibodies against SP CP but not antibodies against keyhole limpet hemocyanin recognized a molecule on the surface of IM-9 cells. Anti-SP CP binding to IM-9 cells was blocked with excess SP antagonist, suggesting that the antibody and the SP antagonist were competing for the same binding site. In support of this possibility, anti-SP CP antibodies blocked 3H-SP binding to IM-9 cells. An immunoaffinity column coupled with antibodies against SP CP bound protein from solubilized IM-9 cells. This isolated protein bound 125I-Tyr8-SP and binding was specifically blocked with SP as well as by SP antagonist, neurokinin A, and eledoisin. Passthrough material did not bind SP suggesting that a SP receptor had been purified. Western blot analysis of solubilized IM-9 cell proteins using anti-SP CP antibodies but not preimmune IgG recognized a single protein of 58,000 D. Taken together, these results demonstrate that antibodies against SP CP recognize a SP receptor present on the lymphocyte cell line, IM-9.

Differential expression of functional adrenocorticotropic hormone receptors by subpopulations of lymphocytes

In an effort to investigate the presence of adrenocorticotropic hormone (ACTH) receptors on rat lymphocytes, cells were separated by a panning procedure into T and B cell populations. By using the radiolabeled ACTH agonist, (125I-Tyr23) phenylalanine2-norleucine4-ACTH1-24, substantial numbers of ACTH binding sites were detected on T and B lymphocytes, but not on thymocytes. Scatchard analysis revealed two types of binding sites on each cell population, one with Kd1 = 0.088 +/- 0.025 nM and one with Kd2 = 4.2 +/- 0.6 nM; however, the absolute number of binding sites per cell was different. B lymphocytes expressed approximately three times the number of Kd1 binding sites per cell when compared with T lymphocytes. However, ACTH receptor expression by these cell populations was not static as suggested by the ability to induce receptor expression via mitogens. B or T cells and thymocytes stimulated with the mitogens LPS or Con A, respectively, substantially increased their number of Kd1 binding sites per cell (approximately three-fold). Even more dramatic increases in Kd1 receptor expression (approximately 100-fold) were observed when comparing "normal" and stimulated thymocytes. To demonstrate that these ACTH binding sites were in fact functional, cAMP levels were measured in lymphocytes 10 min after exposure to varying concentrations of ACTH. Dose-dependent increases in cAMP levels were observed, with significant stimulation occurring with as little as 0.1 nM ACTH added. Taken together, these studies demonstrate the presence of functional ACTH receptors on normal, rat T and B lymphocytes.

Differential expression of functional adrenocorticotropic hormone receptors by subpopulations of lymphocytes

In an effort to investigate the presence of adrenocorticotropic hormone (ACTH) receptors on rat lymphocytes, cells were separated by a panning procedure into T and B cell populations. By using the radiolabeled ACTH agonist, (125I-Tyr23) phenylalanine2-norleucine4-ACTH1-24, substantial numbers of ACTH binding sites were detected on T and B lymphocytes, but not on thymocytes. Scatchard analysis revealed two types of binding sites on each cell population, one with Kd1 = 0.088 +/- 0.025 nM and one with Kd2 = 4.2 +/- 0.6 nM; however, the absolute number of binding sites per cell was different. B lymphocytes expressed approximately three times the number of Kd1 binding sites per cell when compared with T lymphocytes. However, ACTH receptor expression by these cell populations was not static as suggested by the ability to induce receptor expression via mitogens. B or T cells and thymocytes stimulated with the mitogens LPS or Con A, respectively, substantially increased their number of Kd1 binding sites per cell (approximately three-fold). Even more dramatic increases in Kd1 receptor expression (approximately 100-fold) were observed when comparing "normal" and stimulated thymocytes. To demonstrate that these ACTH binding sites were in fact functional, cAMP levels were measured in lymphocytes 10 min after exposure to varying concentrations of ACTH. Dose-dependent increases in cAMP levels were observed, with significant stimulation occurring with as little as 0.1 nM ACTH added. Taken together, these studies demonstrate the presence of functional ACTH receptors on normal, rat T and B lymphocytes.

Anti-peptide antibodies recognize anti-substance P antibodies in an idiotypic fashion

A peptide (AGFGVVKKPNY) was synthesized based on an RNA sequence complementary to the mRNA encoding substance P (Sub P). Antibodies against this Sub P complementary peptide (termed anti-C Pep antibodies) were produced by immunizing rats with peptide conjugated to the carrier protein, keyhole limpet hemocyanin. Antisera were then passed over a peptide conjugated affinity column to specifically purify the anti-C Pep antibodies. In a similar manner, anti-Sub P antibodies were produced in rabbits and made monospecific by affinity chromatography. Using a radioimmunoassay, 125I-anti-C Pep antibodies were found to bind anti-Sub P antibodies in a dose-dependent fashion. Control antibodies did not bind nor did they inhibit binding, suggesting that the interaction of the affinity purified antibodies was not due to the presence of constant region determinants. Ultimately, the idiotypic-anti-idiotypic nature of the anti-Sub P and anti-C Pep antibodies was demonstrated using a radioimmunoassay for Sub P. Anti-C Pep antibodies competed like unlabeled Sub P in the ability to block 125I-Tyr8-Sub P binding to anti-Sub P antibodies, whereas control antibodies did not. We concluded, therefore, that immunizing with this pair of complementary peptides (i.e., Sub P and C Pep) generates antibodies which are anti-idiotypic.