An immunologic network

Long-Term Consequences of Placental Vascular Pathology on the Maternal and Offspring Cardiovascular Systems

Over the last thirty years, evidence has been accumulating that Hypertensive Disorders of Pregnancy (HDP) and, specifically, Preeclampsia (PE) produce not only long-term effects on the pregnant woman, but have also lasting consequences for the fetus. At the core of these consequences is the phenomenon known as defective deep placentation, being present in virtually every major obstetrical syndrome. The profound placental vascular lesions characteristic of this pathology can induce long-term adverse consequences for the pregnant woman's entire arterial system. In addition, placental growth restriction and function can, in turn, cause a decreased blood supply to the fetus, with long-lasting effects. Women with a history of HDP have an increased risk of Cardiovascular Diseases (CVD) compared with women with normal pregnancies. Specifically, these subjects are at a future higher risk of: Hypertension; Coronary artery disease; Heart failure; Peripheral vascular disease; Cerebrovascular accidents (Stroke); CVD-related mortality. Vascular pathology in pregnancy and CVD may share a common etiology and may have common risk factors, which are unmasked by the "stress" of pregnancy. It is also possible that the future occurrence of a CVD may be the consequence of endothelial dysfunction generated by pregnancy-induced hypertension that persists after delivery. Although biochemical and biophysical markers of PE abound, information on markers for a comparative evaluation in the various groups is still lacking. Long-term consequences for the fetus are an integral part of the theory of a fetal origin of a number of adult diseases, known as the Barker hypothesis. Indeed, intrauterine malnutrition and fetal growth restriction represent significant risk factors for the development of chronic hypertension, diabetes, stroke and death from coronary artery disease in adults. Other factors will also influence the development later in life of hypertension, coronary and myocardial disease; they include parental genetic disposition, epigenetic modifications, endothelial dysfunction, concurrent intrauterine exposures, and the lifestyle of the affected individual.

Immunity by equilibrium

The classical model of immunity posits that the immune system reacts to pathogens and injury and restores homeostasis. Indeed, a century of research has uncovered the means and mechanisms by which the immune system recognizes danger and regulates its own activity. However, this classical model does not fully explain complex phenomena, such as tolerance, allergy, the increased prevalence of inflammatory pathologies in industrialized nations and immunity to multiple infections. In this Essay, I propose a model of immunity that is based on equilibrium, in which the healthy immune system is always active and in a state of dynamic equilibrium between antagonistic types of response. This equilibrium is regulated both by the internal milieu and by the microbial environment. As a result, alteration of the internal milieu or microbial environment leads to immune disequilibrium, which determines tolerance, protective immunity and inflammatory pathology.

Substance P signaling mediates BMP-dependent heterotopic ossification

Heterotopic ossification (HO) is a disabling condition associated with neurologic injury, inflammation, and overactive bone morphogenetic protein (BMP) signaling. The inductive factors involved in lesion formation are unknown. We found that the expression of the neuro-inflammatory factor Substance P (SP) is dramatically increased in early lesional tissue in patients who have either fibrodysplasia ossificans progressiva (FOP) or acquired HO, and in three independent mouse models of HO. In Nse-BMP4, a mouse model of HO, robust HO forms in response to tissue injury; however, null mutations of the preprotachykinin (PPT) gene encoding SP prevent HO. Importantly, ablation of SP(+) sensory neurons, treatment with an antagonist of SP receptor NK1r, deletion of NK1r gene, or genetic down-regulation of NK1r-expressing mast cells also profoundly inhibit injury-induced HO. These observations establish a potent neuro-inflammatory induction and amplification circuit for BMP-dependent HO lesion formation, and identify novel molecular targets for prevention of HO.

Genetic and epigenetic regulation schemes: need for an alternative paradigm

Self-organization of living cells results from the tangle of positive and negative feedback developed to ensure their homeostasis and/or their differentiation. There are three major means cellular regulation operates: the genetic, the epigenetic, and the metabolic ones. The regulation type in each of them has been overviewed. Further examination of relations between complexity and developmental stability points out sui generis properties of feedback loops, which are redundancy and pleiotropy. Prototypical schemes for positive and negative regulation with redundant and pleiotropic (including multifunctional) proteins are presented. They stress a theoretical shift from the analytical to the systemic framework. The systemic paradigm appears to be of increasing interest and importance in the study of concepts for the representation of genetic and epigenetic regulations.

Structural basis of stimulatory anti-idiotypic antibodies

In order to design and produce effective vaccines based upon the idiotype network hypothesis of Jerne, a thorough understanding of the biological and structural aspects underlying the stimulating activities of anti-idiotypic antibodies is needed. Here we determined the nucleotide sequence of the variable heavy and light chain regions of two monoclonal anti-idiotypic antibodies which induce different anti-phosphorylcholine responses. The nucleotide sequences of the variable domains of two monoclonal anti-TEPC 15 (T15) antibodies (F6-3 and 4C11) were determined by the primer extension and Maxam-Gilbert techniques. The nucleotide sequence data show that 4C11 and F6-3 have homologous VH segments and JH segments, but different D regions. The VH segments of both clones belongs to the J558 VH family. Most of the differences among the VH segments are located in CDR2. The VK segments of 4C11 and F6-3 are homologous to the VK gene group 4 and group 8, respectively. Comparison of the sequences of 4C11 and F6-3 with other published anti-idiotype antibodies shows that there is no preferential utilization of immunoglobulin genes. An analysis of the distribution of charged residues and hydropathic comparison studies were used to interpret the sequence of 4C11 in terms of the biological mimicry of antigenic stimulation.

Immunoglobulin with complementary paratope and idiotope

A hybridoma antibody (11E7-1) was isolated from a myeloma fusion with nu/nu BALB/c immunized against the T15 idiotype. This IgM antibody exhibited a dual specificity, binding both to PC and to anti-PC antibodies from two idiotype families. Binding to PC and anti-PC antibodies are completely inhibited by PC analogs. Furthermore, the hybridoma antibody binds to itself. Self-binding is also inhibited by PC analogs. From these data, we suggest that 11E7-1 hybridoma antibody has a PC-specific paratope site, and at same time expresses the internal PC antigen idiotope. The term autobody is proposed to signify its self-binding and potential role in autoimmunity. Autobodies may have a unique role in the network of immune system. Furthermore, it may be a model for designing idiotype vaccines.

Acceptor-suppressor T cell hybridoma with a receptor recognizing antigen-specific suppressor factor

An acceptor hybridoma with a receptor that recognizes the keyhole limpet hemocyanin (KLH)-specific suppressor T cell factor (KLH-TsF) was established after the fusion of C57BL/6 splenic T cells enriched with KLH-coated petri dishes. The cloned hybridoma (34S-281) could be specifically activated by stimulation with the conventional KLH-TsF or monoclonal KLH-TsF from three different hybridomas in the absence of the relevant antigen (KLH) and it started to produce another factor that suppresses the antibody response against DNP-KLH in a KLH-specific fashion. The KLH specificity of the TsF was required for activation. The new factor was found not to bind the KLH but to be absorbed with the KLH-TsF-producing hybridoma. It is thus strongly suggested that the acceptor site has a complementary structure (antiidiotype) for the KLH-TsF. Moreover, the idiotypic determinant on KLH-TsF was found to have a structure similar to that on some of the anti-KLH antibodies, since the acceptor hybridoma was specifically killed by the conventional anti-KLH antibodies and complement. Drawing on the above results, the idiotype-antiidiotype network in the conventional antigen system is discussed.

Idiotype-recognizing T helper cells that are not idiotype specific

In this study T helper cells that recognize idiotypes as carriers for a hapten-specific B cell response were analyzed under limiting dilution conditions. T helper cells, induced by phosphorylcholine-hemocyanin (PC-Hy) priming, recognize trinitrophenylated TEPC-15 and MOPC-167 (TNP-T15, TNP-167) equally well. Limiting dilution analysis indicates identical frequencies of helper cells for TNP-T15 and TNP-167. Double immunization protocols using TNP-T15 and TNP-167 fail to demonstrate additive effects. Inhibition of carrier recognition in vitro using free hapten, PC, and unconjugated T15 or M167 indicates identical specificities of helper cells for T15 and M167. Collectively, these results provide strong evidence that PC-Hy priming induces only one population of idiotype-recognizing helper cells that are unable to distinguish between the T15 and the M167 idiotopes. The helper cell induction circuit was further analyzed. PC-Hy priming induces T15/167-specific helper T cells in X-linked immune defect-expressing F1 mice. This indicates that a B cell response to PC is not required to induce idiotype-recognizing T cells. Adoptive cotransfer of B cells from PC-Hy-primed mice together with normal T cells fails to induce idiotype-recognizing T cells. These results indicate the existence of a T helper1-T helper2 induction loop. In this scheme, the T helper1 cell carries T15-like receptors and the T helper2 cells, anti-T15-like receptors. Monoclonal antiidiotypic antibodies specific for T15 also induce a T15/167-recognizing T helper cell population. This finding demonstrates that idiotope-specific priming induces non-idiotype-specific T cells. Evidently, the idiotypic T cell network is based on a different selection of idiotope determinants than the selection of the B cell idiotype network.

Immunotherapeutic potential of idiotype/anti-idiotype regulation of the IgE response

Studies of the induction of suppressor cells by soluble factors and anti-idiotypic antibody in mice have progressed to the point where it now seems likely that patients' allergic responses to grass pollen can be reduced by manipulation through the idiotype-anti-idiotype network.

Induction of a cross-reactive idiotype dextran-positive antibody response in two IgH-Cb mouse strains treated with anti-J558 cross-reactive idiotype antibodies

The effect of IdX-specific rabbit and allogeneic antiidiotype antibodies (Ab2) was investigated in vivo in Igh-Cb mouse strains with respect to the induction of a cross-reactive idiotype (IdX)-positive anti-alpha (1-3) Dextran (Dex) response. These C.B20 and C57Bl/6 mice have an allotype-linked incapacity to respond with IdX-positive anti-alpha (1-3) Dex antibodies upon conventional immunization with Dex B1355. 7 d after the rabbit Ab2 injections, IdX-positive Ig (Ab3) and IdX-positive anti-alpha (1-3) Dex antibodies (Ab1') were detected in the sera of each tested mouse. The affinity-purified Ab1' were idiotypically indistinguishable from reference BALB/c IdX-positive myeloma proteins and BALB/c anti-alpha (1-3) Dex antibodies (Ab1) in a competitive inhibition radioimmunoassay, while Ab3 Ig appeared idiotypically deficient and did not bind to Dex. The response to the alpha (1-6) linkage of Dex was not affected in these mice. A large fraction of the Ab1' and Ab3 responses of both mouse strains were of the IgG1 class. The Ab1' antibodies differed from BALB/c Ab1 by lower relative binding to five of eight tested Dex, and by expressing the Igh4b allotype determinants on the IgG1 antibodies. This study identifies the products of a VHDex gene that appears to be under regulatory control in the Ighb mice. Its association with the b haplotype suggests that this gene may differ structurally from the BALB/c VHDex gene.

High-dose intravenous IgG in adults with autoimmune thrombocytopenia

A study of the effect of high-dose intravenous IgG in 25 adults with autoimmune thrombocytopenia confirmed the predictable rise in the platelet count seen during the infusion and previously reported in children. Unlike the data based on children, there was no sustained response unless the IgG infusion was closely associated with splenectomy. There was no correlation between the presence of platelet autoantibodies or the Ig class of the autoantibody and the pattern of response to the infusion. The initial platelet response appears to be the result of transient blockade of the reticuloendothelial system, including the macrophage Fc receptor mechanism. The long-term response in some patients requires another explanation and may be due to a more specific immunosuppressive effect of the high-dose IgG infusion. Splenectomy may have an additive effect by removing a major site of platelet autoantibody production.

Blood and lymph node T-lymphocyte subsets in non-Hodgkin lymphomas

Blood and lymph node T-lymphocyte subpopulations have been studied in untreated non-Hodgkin lymphoma (NHL) patients and healthy controls. T-lymphocytes were determined by the E-rosette technique and by OKT3/LEU4 monoclonal antibodies; OKT4/LEU3 and OKT8/LEU2 monoclonal antibodies were used to identify T-cell subsets with helper/inducer and suppressor/cytotoxic activity, respectively. OKT4+ T-cells were low in patients, while OKT8+ T-cell numbers were normal. The OKT4+/OKT8+ blood lymphocyte ratio was below the normal range in about 50% of the patients. The ratio was higher in lymph nodes than in blood of patients and controls. The results may suggest that untreated NHL patients have a reduced pool of T-cells with phenotypic markers of OKT4/LEU3. Monoclonal blood B-lymphocytes were found in 45% of the cases. The presence of such cells in blood was frequently associated with a low OKT4+/OKT8+ ratio.

Immunoregulation of murine myeloma in vitro. II. Suppression of MOPC-315 immunoglobulin secretion and synthesis by idiotype-specific suppressor T cells

In previous studies, BALB/c mice immunized with trinitrophenyl-specific IgA protein (M315) produced by MOPC-315 developed idiotype (Id315)-specific T cells that suppressed M315 secretion in vivo. In the present in vitro studies, we show that inhibition of M315 secretion is mediated by a theta,Lyt-1-2+ cell that expresses a surface membrane receptor for Id315. The suppressor signal is a diffusable product that acts directly on M315-secreting myeloma cells. Inhibition of M315 secretion is T cell dose-dependent, Id315-specific, reversible, and occurs without any effect on MOPC-315 growth, viability, or surface membrane expression of M315. Inhibition of M315 secretion results from a selective inhibition of M315 synthesis in the myeloma cell. These studies provide new insight into the mechanisms of direct B cell regulation by idiotype-specific T cells.

Biologic activity of anti-thyrotropin anti-idiotypic antibody

We raised an antihuman thyrotropin anti-idiotypic antibody and showed that it was active at the thyrotropin receptor. Thus this antibody inhibited 125I b-TSH binding to thyroid plasma membranes, stimulated adenylate cyclase activity through a guanyl nucleotide-dependent mechanism, increased radioiodide entry rate into isolated porcine thyroid follicular cells, and induced such cultured cells to organize into follicles. All these parameters are typical of thyrotropin action. This work raises the possibility that thyroid stimulating antibodies that cause the hyperthyroidism of Graves disease may be, at least in some patients, anti-thyrotropin anti-idiotypic antibodies. It also offers a novel method whereby antireceptor antibodies used in the isolation and characterization of the receptor may be raised from ligands.

Suppression of interstitial nephritis by auto-anti-idiotypic immunity

Rats immunized with renal tubular antigens were protected from the development of interstitial nephritis by pretreatment with tubular antigen-reactive T lymphoblasts. Protected animals developed anti-idiotypic antibodies against idiotypes primarily within the antigen-binding region of monoclonal antitubular basement membrane antibodies. These studies extend the concept of auto-anti-idiotypic regulation to autoimmune disease, and they also provide an experimental basis for further efforts to develop biologically relevant mechanisms for attenuating the expression of other kidney diseases.

Regulation by complementary idiotypes. Ig protects the clone producing it

A/He mice actively producing complementary or anti-idiotypic antibody directed against a combining site structure for phosphorylcholine (PC) have profound and long-lasting suppression of their response to PC. B cells from unresponsive mice are unresponsive in vitro, and attempts to demonstrate suppressor cells in unresponsive mice were unsuccessful. Although the process ultimately responsible for suppression has not been defined, suppression can be initiated by anti-idiotypic antibody alone and prevented by complementary Ig; i.e., by anti-PC antibody. Furthermore, a suppressed anti-PC response can be rescued by sublethal irradiation and anti-PC antibody given passively. The recovery of the suppressed response is slow and presumably results from maturation from "stem" cells, which are protected from tolerization by the passively given antibody. Thus, by extrapolation, one of the functions of secreted Ig may be to protect the clone that produces it.