The interleukin-2 receptor

Modulation of interleukin 2 high affinity binding to human T cells by a pyrimidodiazepine insect metabolite

An insect metabolite containing the little known pyrimido[4,5-b][1,4]diazepine ring system has been found to act as an effective mimic of tetrahydrobiopterin in its ability to modulate the affinity of interleukin 2 (IL-2) for its receptors on human T cells. Semi-empirical molecular orbital calculations reveal that while tetrahydrobiopterin has considerable flexibility, the pyrimidodiazepine has rather few conformational options and offers a useful model for exploring the nature of the pterin binding site.

Ulcerative colitis-like disease in mice with a disrupted interleukin-2 gene

Mice deficient for interleukin-2 develop normally during the first 3-4 weeks of age. However, later on they become severely compromised, and about 50% of the animals die between 4 and 9 weeks after birth. Of the remaining mice, 100% develop an inflammatory bowel disease with striking clinical and histological similarity to ulcerative colitis in humans. The alterations of the immune system are characterized by a high number of activated T and B cells, elevated immunoglobulin secretion, anti-colon antibodies, and aberrant expression of class II major histocompatibility complex molecules. The data provide evidence for a primary role of the immune system in the etiology of ulcerative colitis and strongly suggest that the disease results from an abnormal immune response to a normal antigenic stimulus.

Does oligosaccharide-phosphatidylinositol (glycosyl-phosphatidylinositol) hydrolysis mediate prolactin signal transduction in granulosa cells?

Initial biosynthetic radiolabelling experiments with cultured granulosa cells revealed the presence of an oligosaccharide-phosphatidylinositol (glycosyl-phosphatidylinositol; (Ose)nPtdIns) structurally related to (Ose)nPtdIns-lipids isolated from other cell types. Prolactin (PRL) stimulated [3H]glucosamine-(Ose)nPtdIns turnover and the rapid generation of [3H]myristoyl-diacylglycerol in cultured follicle-stimulating hormone-(FSH)-primed granulosa cells endowed with PRL receptors. In parallel experiments performed with [3H]myo-inositol-labelled granulosa cells, treatment with PRL stimulated (Ose)nPtdIns hydrolysis in a similar manner, whereas no effect on phosphoinositide (PtdIns, PtdInsP and PtdInsP2) turnover could be observed. These results strongly suggest that the cleavage of (Ose)nPtdIns by phosphodiesterase followed by the subsequent generation of diacylglycerol and a soluble phosphoinositol-oligosaccharide (inositol-phosphoglycan; (Ose)nInsP) moiety could be part of the signal-transduction mechanism linking PRL receptors to their biological effects in granulosa cells. To test this hypothesis, we examined the effect of PRL and purified (Ose)nInsP moiety (from rat liver membranes) on granulosa cell 3 beta-hydroxysteroid dehydrogenase/delta 5-4 isomerase (3 beta-HSD) enzyme activity. Results presented show that, in FSH-primed granulosa cells, PRL (40 nM) and (Ose)nInsP (5 microM) prevented gonadotropin-stimulated 3 beta-HSD activity. Furthermore, in undifferentiated granulosa cells where PRL receptors are absent, no effect of the hormone on 3 beta-HSD activity could be observed, whereas (Ose)nInsP (1-10 microM) inhibited enzyme activity in a dose-dependent manner.

Expression of human IL-2 receptor alpha- and beta-chains using the baculovirus expression system

The genes encoding the alpha- and beta-chains of the human interleukin-2 receptor were expressed in lepidopteran insect cells using the baculovirus expression vector system. The corresponding genes were inserted under the polyhedrin promoter of the Autographa california nuclear polyhedrosis virus and expressed in the Spodoptera frugiperda insect cell line during viral infection. The recombinant receptor proteins were identified in the insect cell lysates by using protein dot blot and ELISA techniques. At 36 h post infection the corresponding proteins were clearly detected using anti-IL-2 alpha- and beta-receptor-specific antibodies. A large amount of the alpha-chain was also found in the supernatant culture media at 72 h post infection and metabolic labelling with [35S]-methionine indicated that it was proteolytically cleaved into a 32 kDa soluble form. A similar soluble or secreted form of the beta-chain was, however, not observed. Both receptor proteins were expressed on the surface of the insect cells as determined by flow cytometry analysis. Studies performed with the different IL-2 receptor forms (alpha- and beta-chains alone or in combination) in the presence or absence of rIL-2 suggest that the receptor proteins when expressed in infected insect cells are non-functional with respect to tyrosine phosphorylation.

Electroblotting proteolytic products from native gel for direct N-terminal sequence analysis: an approach for studying protein-protein interaction

Proteins which are electroblotted from native gels onto polyvinylidene difluoride (PVDF) membranes are suitable for detailed structural analysis. This method, in conjunction with limited proteolysis and N-terminal sequencing, has been used to study the molecular interactions between native protein molecules. The interaction between recombinant interleukin-2 (rIL-2) and its receptor (rIL-2R alpha) was examined as a model system. The working strategy consists of (i) proteolysis of rIL-2R alpha and rIL-2R alpha/rIL-2 complex, (ii) separation of the major proteolytic products by native polyacrylamide gel electrophoresis followed by electroblotting onto PVDF membrane, and (iii) sequence analysis of the blotted protein bands for the identification of peptide regions sensitive to proteolysis. Results have indicated that the exon 3 encoded region in rIL-2R alpha is sensitive to proteolysis regardless whether it is complexed with rIL-2 or not. This suggests that no major conformational changes occur in rIL-2R alpha during interaction with rIL-2. This electroblotting approach is, therefore, useful for studying protein-protein interaction in solution.

Human melanoma cells express a functional interleukin-2 receptor

Flow cytometric analysis reveals that 5 human melanoma cell lines (M14, IGR3, ME1477, JUSO, GLL19) express both alpha and beta chain of the interleukin 2 receptor (IL-2R alpha and IL-2R beta). These chains are able to specifically bind IL-2 and to form high-affinity heterodimers (IL-2R alpha beta). Analysis of poly A+ RNAs by Northern blot reveals the presence of typical transcripts for both the IL-2R alpha gene (3.6 kb) and the IL-2R beta gene (4 kb). Reverse transcription/polymerase chain reaction analysis allowed transcripts for the IL2R gamma (p64) gene to be detected in 3 of these melanoma cell lines (M14, IGR3, ME 1477). Incubation with human recombinant IL-2 modifies in IL-2R alpha+beta+gamma+ (M14) the expression of several surface molecules: down-regulation of ICAM-1, HLA class I and HLA-DR and up-regulation of CD44. IL-2 is also active on IL-2 alpha+beta+gamma- cell lines since it decreases ICAM-1 and HLA class-II expression at the surface of JUSO cells. Down-regulation of ICAM-1, whose expression in melanoma cells is a marker of tumor progression, is detectable within 3 hr in M14 cells and is maximal after 48 hr incubation, at IL-2 concentrations corresponding to the high-affinity heterodimers. This feature is specific since it is partially inhibited by MAbs directed against the IL-2 binding site of the IL-2R alpha (MAR93, 10T14) and IL-2R beta (MiK beta 1, TU27) chains. Our data support the notion of a direct effect of IL-2 on human melanoma cells. Modulation of the expression of surface molecules which is important for the interaction with immunocompetent cells or for tumor progression, could have a role to play during in vivo IL-2 treatment of human melanomas.

The IL-2/IL-2 receptor system: a target for rational immune intervention

The expression of interleukin 2 (IL-2), induction of its multisubunit receptor and subsequent interplay of this ligand with its receptor are pivotal events in T-cell activation. Our present understanding of the normal IL-2/IL-2R system and of disorders in this network in disease opens the possibility for more specific immune intervention. Thomas Waldmann discusses the clinical application of IL-2, agents that inhibit IL-2 synthesis and action, and how the anti-IL-2 receptor-directed therapy provides a novel perspective for prevention of allograft rejection and for treatment of graft versus host disease, select autoimmune disorders and certain neoplastic diseases.

The IL-2/IL-2 receptor system: a target for rational immune intervention

The expression of interleukin 2 (IL-2), induction of its multisubunit receptor and subsequent interplay of this ligand with its receptor are pivotal events in T-cell activation. Our present understanding of the normal IL-2/IL-2 receptor system, and of disorders in this network in disease, opens the possibility for more specific immune intervention. Thomas Waldmann discusses how the clinical application of IL-2, agents that inhibit IL-2 synthesis and action, and anti-IL-2 receptor-directed therapy provide a novel perspective for prevention of allograft rejection and for treatment of graft-versus-host disease, select autoimmune disorders and certain neoplastic diseases.

Identification and purification of a receptor on macrophages for the dengue virus-induced suppressor cytokine

Dengue type 2 virus (DV)-induced suppressor cytokine (SF) binds to macrophages to transmit the suppressor signal to recruit the second subpopulation of suppressor T cells. The present study was undertaken to identify and purify the receptor for SF (SF-R) on macrophages. The binding of 125I-SF to macrophages was saturable and reversible. Scatchard analysis showed the presence of both high (54,000/cell) and low (1.78 x 10(6)/cell) affinity receptor sites. The binding of 125I-SF to macrophages was inhibited by pretreatment of macrophages with anti-SF antiserum but not by a heterologous antiserum. Normal mouse peritoneal macrophage membrane was solubilized with Triton-X-100 and the components separated by low pressure liquid chromatography (LPLC) to purify SF-R. The presence of SF binding moiety (SF-R) was screened at each step of purification. The purified SF-R resolved into two bands of 45-50 kD mol. wt on SDS-PAGE. 125I-SF+SF-R complex run on SDS-PAGE showed a single band at about 55-60 kD mol. wt by autoradiography. Anti-SF-R antiserum reacted with SF-R in a Western blot test; the reaction was abolished by pretreatment of the blots with proteinase K, but not by pretreatment with periodic acid. SF-R was composed of two polypeptide chains (alpha and beta) which were obtained in pure form by high performance liquid chromatography (HPLC) of dithiothreitol- and iodoacetamide-treated SF-R. Only the beta chain bound SF.

Changing patterns of the IL-2/IL-2R pathway of lymphocyte activation following exposure to Plasmodium falciparum products: a study with squirrel monkey peripheral blood mononuclear cells

Squirrel monkeys are experimental hosts useful for studies on human malaria. In the present work, in vitro lymphocyte reactivity was measured by proliferation in the presence of Plasmodium falciparum-derived products, and found to depend on the previous malarial status of the animals and upon the source and/or the nature of the P. falciparum-derived material. Special attention was given to the IL-2/IL-2R pathway of lymphocyte activation. Culture supernatant from P. falciparum-parasitized erythrocytes exerted an inhibitory effect towards T lymphocytes obtained from P. falciparum-non-immune squirrel monkeys, when activated, for instance, by PHA. These lymphocytes did not incorporate tritiated thymidine (neither they did proliferate) although they expressed IL-2 alpha and beta binding chains and secreted IL-2 (or at least TCGF). This inhibitory effect could not be rescued by the addition of rhIL-2, although the assayed lymphocytes could retain the ability to continue their cell cycle progression and divide after removal of the P. falciparum-derived inhibitory product(s). The incidence of anti-mitogenic molecules which impair the IL-2/IL-2R pathway of lymphocyte activation in malaria related processes is discussed.

A monoclonal antibody which inhibits growth of T cell lines

In an attempt to elucidate the intricate structure and possibly the signal transduction pathway of the interleukin-2 receptor (IL-2R) we tried to produce monoclonal antibodies against putative human IL-2R-associated molecules which precipitated from YT2C2 cells with a monoclonal antibody (Mik beta 3) against the human IL-2R beta chain. One of the antibodies obtained (7 x A10) recognizes a cell surface molecule of about 120 kDa (p120). Cross-linking of [125I]-IL-2 and immunoprecipitation with 7 x A10 suggest that the p120 protein may somehow associate physically with the IL-2R beta chain. Although p120 itself did not bind IL-2, and 7 x A10 did not inhibit IL-2 binding to the IL-2R, growth of the human IL-2-dependent cell lines ED40515 and Kit225 was completely inhibited by adding 7 x A10 to the culture at a relatively low concentration (0.2 micrograms/ml). At a higher concentration (2 micrograms/ml) 7 x A10 inhibited the growth of YTC3 and YT2C2 cells expressing IL-2Rs with high and intermediate affinities, respectively. The B cell line FLEB-14 and the erythroid cell line K562, which both express p120 as determined by flow cytometry, but no IL-2R alpha or beta chains showed only slight proliferation changes at high 7 x A10 concentrations. Out of 16 lymphocyte cell lines tested so far, only Molt-4, Raji and Daudi did not express p120, and therefore 7 x A10 did not influence their growth behavior.(ABSTRACT TRUNCATED AT 250 WORDS)

Combinatorial functions of two chimeric antibodies directed to human CD4 and one directed to the alpha-chain of the human interleukin-2 receptor

The general feasibility of chimerization of monoclonal antibodies (mAbs) has already been shown for a large number of them. In order to evaluate in vitro parameters relevant to immunosuppressive therapy, we have chimerized and synthesized two anti-CD4 mAbs recognizing two different epitopes on the human T-lymphocyte antigen, CD4. The chimerized mAbs are produced at levels corresponding to those of the original hybridoma cell lines. With respect to activation of human complement, the individual Abs are negative; however, when used in combination, complement activation was performed. When applied in combination, they were found to modulate the CD4 antigen, whereas the individual mAb do not display this property. Individually they mediate an up to 60% inhibition of the mixed lymphocyte reaction (MLR). However, by combination of an anti-CD4 mAb with one directed against the alpha-chain of the human IL2 receptor, nearly 100% inhibition of the MLR was achieved, even with reduced dosage of the mAbs. Our data suggest that the combination of an anti-CD4 mAb and an anti-IL2R alpha chain mAb is more effective with respect to immunosuppression than each mAb by itself, indicating that this mAb cocktail could be a new strategy for immunosuppressive therapy.

Cytokine receptors: structure and signal transduction

In the past 2-3 years, a number of cytokine receptors have been partly characterized and the cDNAs for the ligand binding chains cloned. This has revealed that cytokine receptors are complex. Many are known to be multichain receptors (e.g. IL-2) and since their mechanism of signal transduction is not obvious, it is likely that other proteins yet to be defined take part in the signalling process. The cloning of the receptor ligand binding chain has revealed that (unlike cytokines), there are major families of receptors. Some are members of the Ig supergene family (e.g. IL-1 receptor), others are members of the nerve growth factor receptor family (e.g. TNF), but the majority are members of the haematopoietic growth factor family (e.g. IL-3, GM-CSF). Yet other cytokine receptors do not belong to a family, e.g. IFN-gamma.

Analysis of IL-2 functional structure by multiple cysteine substitutions

IL-2 has three cysteine residues. The cysteines at positions 58 and 105 of active IL-2 form an intramolecular disulfide bond while that at position 125 remains as a free form. To evaluate the importance of correct disulfide bond, mutant proteins (muteins) that have triple and double substitutions of cysteines with alanines, namely A58/105/125 and A58/125, were made by polymerase chain reaction method respectively. Thymidine incorporation assay on CTLL-2 cells showed that although these two muteins were only 0.5-2.0% as potent as that of wild type IL-2, they were 50-200 fold more active than A58, a mutein that has substitution of cysteine at position 58 with alanine. Binding inhibition study showed that the relative affinity of muteins A58/125 and A58/105/125 for high affinity IL-2 receptors was 5-25 fold higher than that of A58. These results suggest that the dramatic decrease in the activity of mutein A58 may result from the formation of an incorrect disulfide bond between the cysteines at positions 105 and 125.

Interleukin-6 and its receptor: a paradigm for cytokines

Many cytokines and cytokine receptors involved in the regulation of hematopoiesis, immune responses, and inflammation have been identified and characterized at the molecular level. Several characteristic features of cytokines, such as pleiotropy and redundancy, are now more clearly understood on the basis of their molecular structures. Accumulating evidence has demonstrated an intimate link between cytokines and various diseases such as allergy, autoimmune diseases, and cancer. The pathogenesis of these diseases and therapies to treat them will be discussed based on insights derived from cytokine research.

Effects of glutathione on the synthesis and turnover of interleukin-2 receptors

Internalization of IL-2 is important for its biological activities. The internalization of IL-2 was regulated by the duration of glutathione (GSH) treatment in CTLL-2 and CT-4R cells. Flow cytometric studies showed that the level of surface IL-2 receptors was not increased by GSH treatment. Northern blot analysis showed that the mRNA of IL-2Rp55 and IL-2Rp70, the two major components of the high-affinity IL-2 receptors, was increased 6 hr after GSH treatment. The appearance rate of membrane IL-2 receptors in GSH-treated cells was faster than that of the untreated cells. GSH also shortened the half-life (from 5 to less than or equal to 3 hr) and thus increased the turnover of the surface high-affinity IL-2 receptors. These results suggest that although GSH does not affect the level of surface IL-2 receptors, GSH may regulate the internalization of IL-2 by enhancing the synthesis and turnover of surface IL-2 receptors.

Diseases associated with HTLV-I: virus, IL-2 receptor dysregulation and redox regulation

HTLV-I, the etiological agent in adult T-cell leukemia, has also been strongly implicated in a number of non-neoplastic T-cell-associated diseases. Here, Junji Yodoi and Takashi Uchiyama review these associations and focus on the emerging concepts of IL-2R dysregulation and redox regulation by adult T-cell leukemia-derived factor in the pathogenesis of HTLV-I-related diseases.

Dynamic physical interactions of plasma membrane molecules generate cell surface patterns and regulate cell activation processes

Molecular interaction and transmembrane signal transducing events generate a very dynamic and ever changing "pattern" in the plasma membranes. Lymphocytes, the key functional elements of the immune system, are eminently suited to be the primary targets to investigate these proximity, mobility, or other physical-chemical changes in their plasma membranes. Recently, a number of experiments suggested that processed peptides from antigens can bind specific components of MHC molecules (Elliott et al., 1991). This is certainly a way to alter their structure. Cell surface patterns of topological nature, assembly and disassembly of oligomeric receptor structure like the IL-2 receptor have been investigated by sophisticated biophysical techniques. The dynamic changes in the two-dimensional cell surface pattern and intramolecular conformational changes within this "larger" macro-pattern may have a strong regulatory role in signal transducing and intercellular recognition processes. Recent data on these problems are presented together with brief and critical discussions.

Characterization of human thyrotropin receptor-related peptide-like immunoreactivity in peripheral blood of Graves' disease

An antiserum raised against an alignment of amino acid-(32-56), termed TSHRP-1, in the extracellular domain of human thyrotropin (TSH) receptor was used to identify the TSH receptor-like substance in plasma of Graves' disease. The dilution curve of plasma TSHRP-1-like immunoreactivity was observed in a manner parallel to the standard synthetic peptide curve in radioimmunoassay, and its molecular weight estimated approximately 60 kDa. The amounts of TSHRP-1-like immunoreactivity were significantly higher in Graves' plasma than those in plasma of normal and hypothyroid patients due to Hashimoto's thyroiditis. The present results indicate that human peripheral blood possesses a soluble form of the extracellular domain of TSH receptor which may contribute to the pathophysiology of Graves' disease.

Regulation of interleukin-2 responses by phosphatidic acid

Interleukin-2 (IL-2) plays a central role in the immune system by regulating the proliferation and differentiation of T lymphocytes. However, the molecular mechanism of the signal transduction through the IL-2 receptor is poorly understood. We have studied the role of phosphatidic acid (PA) on IL-2 signal transduction using cloned T lymphocytes. IL-2 stimulated a transient increase in the PA concentration in resting CTLL-2 cells prelabeled with [3H]palmitic acid. This effect was detected as early as 1 min after IL-2 addition and peaked at 5 min. IL-2 similarly increased phospholipase D activity in intact CTLL-2 cells, as inferred by phosphatidylethanol production. By contrast, IL-2 did not affect [3H]palmitic acid-labeled diacylglycerol levels. Furthermore, exogenous addition of several natural or synthetic PA to T cells mimicked IL-2 activity. Thus, PA were able to induce DNA synthesis on CTLL-2 cells, although this effect was only 10%-20% of that observed with IL-2. PA showed a synergistic effect with low doses of IL-2. In addition, PA was able to induce c-myc RNA transcription in CTLL-2 cells as well as IL-2 receptor (CD25) expression on the cell membrane with equal potency as saturating doses of IL-2. It is likely that IL-2-induced PA accumulation is a consequence of phospholipase D activation. This hypothesis is further supported by the fact that the addition of exogenous phospholipase D but not phosphatidylinositol-specific phospholipase C also reproduced the IL-2 or PA effects mentioned above. In summary, our results suggest a role of phospholipase D activation and PA formation as second messengers of IL-2 activity.

T-lymphocyte proliferation: tyrosine kinases in interleukin 2 signal transduction

Interleukin 2 (IL-2)-induced tyrosine phosphorylation appears to play a major role in IL-2-induced cellular proliferation. Several intracellular substrates including the beta chain of the IL-2 receptor complex (IL-2R beta), raf, MAP2 kinase, the regulatory 83 kDa subunit of phosphatidylinositol-3 kinase and S6 kinases are substrates for the IL-2 receptor activated kinase(s). However, none of the identified members of the IL-2 receptor complex exhibits intrinsic tyrosine kinase activity. Therefore, the IL-2R complex must activate intracellular tyrosine kinases. We have demonstrated that specific tyrosine and serine/threonine kinases are coprecipitated with IL-2 receptor constructs that mediate IL-2-induced cell proliferation but not with those that do not. The IL-2-activated tyrosine kinase appears to be associated with a serine and proline rich intracellular domain which is highly conserved between IL-2R beta and the erythropoietin receptor. Although the responsible kinase has not been identified, lck, fyn, fgr, ltk, hck and lyn can be ruled out as obligatory mediators. Using methods to clone tyrosine kinases from T cells, we have identified potential candidate kinases, including several which had not been known to be expressed by T lymphocytes as well as several unique kinases which had not been previously identified in any cell type.

Structural requirements for the modulatory effect of 6-substituted pterins on interleukin 2 receptor binding

(6R)-5,6,7,8-Tetrahydrobiopterin is produced by stimulated human T lymphocytes, and is known to affect various aspects of interleukin-2-directed T cell proliferation. Using an increased apparent affinity of interleukin 2 receptor to interleukin 2 as a measure of activity, this study explores whether other 6-substituted pterins might have the same effect, and what structural features are necessary for activity. Of the compounds tested, only the T-lymphocyte-derived (6R)-5,6,7,8-tetrahydrobiopterin was active. The diastereomeric (6S)-5,6,7,8-tetrahydrobiopterin was inactive, as were 7,8-dihydrobiopterin, sepiapterin, 5,6,7,8-tetrahydroneopterin, 6,7-dimethyl-5,6,7,8-tetrahydropterin and 6-hydroxymethylpterin. 7,8-Dihydroneopterin and neopterin were also found to be inactive. It follows that neither of these compounds participates in the feedback modulation of IL-2 receptor affinity, although both of them can be detected upon IFN-gamma stimulation of human monocytes/macrophages. A computer-based molecular modelling study of (6R)-5,6,7,8-tetrahydrobiopterin and (6R)-5,6,7,8-tetrahydroneopterin revealed substantial differences in overall shape between the two molecules, with certain features figuring prominently in the low-energy conformers of (6R)-5,6,7,8-tetrahydrobiopterin.

Binding of monoclonal anti-interleukin 2 antibody to nucleoli in acute leukemia blast cells

Neutralizing anti-IL-2, anti-IL-3, and anti-IL-6 monoclonal antibodies (MAbs) were used for the immunoenzymatic detection of the respective cytokines in blast cells of 38 patients with acute myeloid (AML) and lymphoid (ALL) leukemias by the APAAP-technique. In 20/24 AML-cases (83%) blast cells showed intranuclear staining with MAb anti-IL-2 (DMS-1). In 17 cases reaction was restricted to the nucleoli, in 4 cases additional cytoplasmic staining was observed. Only 2/13 (15%) of the ALL cases showed anti-IL-2 staining. In contrast to IL-2, neither IL-3, IL-6 nor IL-2R alpha-chains were detected in any of the acute leukemias tested. The anti-IL-2 staining of nucleoli in AML cells is distinct from the cytoplasmic staining which is observed in PHA-activated normal lymphocytes and in a minority of AML cells.

The response of human decidual leukocytes to IL-2

The phenotype of human decidual leukocytes, composed predominantly of CD3-CD16(-)-CD56bright cells, was examined after culture with IL-2 by immunofluorescence and flow cytometry. After IL-2 stimulation the phenotype became like that found on classical NK cells, with an increased proportion of cells expressing CD16. The IL-2R alpha was absent before and after IL-2 stimulation. However, the intermediate affinity receptor, IL-2R beta, was expressed by CD56bright decidual cells, but this receptor was downregulated after IL-2 stimulation. IL-2-induced proliferation of CD56+ decidual cells could be blocked using TU27, a monoclonal antibody to the IL-2R beta. These findings indicate activation of decidual leukocytes by IL-2 occurs through the IL-2R beta alone.

The role of interleukin 2 in the development of autoimmune thyroiditis

Interleukin 2 (IL-2) is a lymphokine that may disrupt immunological self-tolerance. While being incapable of interfering with intrathymic or peripheral clonal deletion, IL-2 may overcome functional antigen unresponsiveness in anergic T lymphocytes. Anergy of T helper cells of the inflammatory phenotype implies selective silencing of the transcription of the IL-2 gene and thus precludes autocrine IL-2/IL-2 receptor (IL-2R) mediated growth, as well as delivery of help to other T cells or B lymphocytes. Thus, IL-2 serves as a servomodulator regulating post-deletional self-tolerance. IL-2-producing and IL-2-receptive cells are present in a variety of autoimmune lesions, including spontaneous autoimmune thyroiditis developing in the Obese strain (OS) of chickens, in Hashimoto's struma lymphomatosa, and in Graves' disease. Whereas the OS is characterized by a hyperinducibility of the IL-2/IL-2R system that predisposes to the development of severe thyroid infiltration, the state of the IL-2/IL-R system in circulating lymphocytes of patients developing thyroid autoimmunity, or at risk of doing so, remains to be defined. The most frequent autoimmune side-effect of IL-2 treatment concerns the thyroid gland. IL-2 induces a lymphoid thyroiditis leading to primary hypothyroidism, especially in those patients that have pre-treatment antithyroid autoantibodies. The hypothesis is extrapolated that IL-2 induces autoimmune disease in those patients that bear undeleted thyroid-specific T cells, and in which the lack of manifest thyroiditis relies upon peripheral, post-deletional tolerance.

Structural analyses of proteins electroblotted from native polyacrylamide gels onto polyvinyldiene difluoride membranes. A method for determining the stoichiometry of protein-protein interaction in solution

The usefulness of a native gel electroblotting technique in the study of protein-protein interactions was demonstrated by the determination of the stoichiometry of the interaction between interleukin-2 (IL-2) and the alpha subunit of IL-2 receptor (IL-2R alpha) in solution. Complexes formed between the recombinant forms of the two proteins in solution were separated from the noncomplexed protein molecules by electrophoresis in a native polyacrylamide gel and the protein bands were electroblotted quantitatively onto polyvinyldiene difluoride membranes for further structural analysis. The data obtained from sequence and amino acid analyses of the blotted proteins provided direct evidence that IL-2 binds to IL-2R alpha in a 1:1 ratio. This methodology should be applicable to the study of other structure/function aspects of protein-protein interactions in solution.

Monoclonal antibodies in diagnosis and therapy

Monoclonal antibodies have been applied clinically to the diagnosis and therapy of an array of human disorders, including cancer and infectious diseases, and have been used for the modulation of immune responses. Effective therapy using unmodified monoclonal antibodies has, however, been elusive. Recently, monoclonal antibody-mediated therapy has been revolutionized by advances such as the definition of cell-surface structures on abnormal cells as targets for effective monoclonal antibody action, genetic engineering to create less immunogenic and more effective monoclonal antibodies, and the arming of such antibodies with toxins or radionuclides to enhance their effector function.