The high affinity interleukin 2 receptor: evidence for three distinct polypeptide chains comprising the high affinity interleukin 2 receptor

The common γ-chain cytokine receptor: tricks-and-treats for T cells

Originally identified as the third subunit of the high-affinity IL-2 receptor complex, the common γ-chain (γc) also acts as a non-redundant receptor subunit for a series of other cytokines, collectively known as γc family cytokines. γc plays essential roles in T cell development and differentiation, so that understanding the molecular basis of its signaling and regulation is a critical issue in T cell immunology. Unlike most other cytokine receptors, γc is thought to be constitutively expressed and limited in its function to the assembly of high-affinity cytokine receptors. Surprisingly, recent studies reported a series of findings that unseat γc as a simple housekeeping gene, and unveiled γc as a new regulatory molecule in T cell activation and differentiation. Cytokine-independent binding of γc to other cytokine receptor subunits suggested a pre-association model of γc with proprietary cytokine receptors. Also, identification of a γc splice isoform revealed expression of soluble γc proteins (sγc). sγc directly interacted with surface IL-2Rβ to suppress IL-2 signaling and to promote pro-inflammatory Th17 cell differentiation. As a result, endogenously produced sγc exacerbated autoimmune inflammatory disease, while the removal of endogenous sγc significantly ameliorated disease outcome. These data provide new insights into the role of both membrane and soluble γc in cytokine signaling, and open new venues to interfere and modulate γc signaling during immune activation. These unexpected discoveries further underscore the perspective that γc biology remains largely uncharted territory that invites further exploration.

Heparin-Binding Epidermal Growth Factor–Like Growth Factor/Diphtheria Toxin Receptor Expression by Acute Myeloid Leukemia Cells

Heparin-binding epidermal growth factor–like growth factor (HB-EGF) is an EGF family member expressed by numerous cell types that binds to EGF receptor 1 (HER-1) or 4 (HER-4) inducing mitogenic and/or chemotactic activities. Membrane-bound HB-EGF retains growth activity and adhesion capabilities and the unique property of being the receptor for diphtheria toxin (DT). The interest in studying HB-EGF in acute leukemia stems from these mitogenic, chemotactic, and receptor functions. We analyzed the expression of HB-EGF in L428, Raji, Jurkat, Karpas 299, L540, 2C8, HL-60, U937, THP-1, ML-3, and K562 cell lines and in primary blasts from 12 acute myeloid leukemia (AML) cases, by reverse-transcriptase polymerase chain reaction (RT-PCR) and Northern blot and by the evaluation of sensitivity to DT. The release of functional HB-EGF was assessed by evaluation of its proliferative effects on the HB-EGF–sensitive Balb/c 3T3 cell line. HB-EGF was expressed by all myeloid and T, but not B (L428, Raji), lymphoid cell lines tested, as well as by the majority (8 of 12) of ex vivo AML blasts. Cell lines (except for the K562 cell line) and AML blasts expressing HB-EGF mRNA underwent apoptotic death following exposure to DT, thus demonstrating the presence of the HB-EGF molecule on their membrane. Leukemic cells also released a fully functional HB-EGF molecule that was mitogenic for the Balb/c 3T3 cell line. Factors relevant to the biology of leukemic growth, such as tumor necrosis factor- (TNF-), 1,25-(OH)2D3, and especially all-trans retinoic acid (ATRA), upregulated HB-EGF mRNA in HL-60 or ML-3 cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) induced HB-EGF mRNA and acquisition of sensitivity to DT in one previously HB-EGF–negative leukemia case. Moreover, the U937 and Karpas 299 cell lines expressed HER-4 mRNA. This work shows that HB-EGF is a growth factor produced by primary leukemic cells and regulated by ATRA, 1,25-(OH)2D3, and GM-CSF.

Heparin-Binding Epidermal Growth Factor–Like Growth Factor/Diphtheria Toxin Receptor Expression by Acute Myeloid Leukemia Cells

Heparin-binding epidermal growth factor–like growth factor (HB-EGF) is an EGF family member expressed by numerous cell types that binds to EGF receptor 1 (HER-1) or 4 (HER-4) inducing mitogenic and/or chemotactic activities. Membrane-bound HB-EGF retains growth activity and adhesion capabilities and the unique property of being the receptor for diphtheria toxin (DT). The interest in studying HB-EGF in acute leukemia stems from these mitogenic, chemotactic, and receptor functions. We analyzed the expression of HB-EGF in L428, Raji, Jurkat, Karpas 299, L540, 2C8, HL-60, U937, THP-1, ML-3, and K562 cell lines and in primary blasts from 12 acute myeloid leukemia (AML) cases, by reverse-transcriptase polymerase chain reaction (RT-PCR) and Northern blot and by the evaluation of sensitivity to DT. The release of functional HB-EGF was assessed by evaluation of its proliferative effects on the HB-EGF–sensitive Balb/c 3T3 cell line. HB-EGF was expressed by all myeloid and T, but not B (L428, Raji), lymphoid cell lines tested, as well as by the majority (8 of 12) of ex vivo AML blasts. Cell lines (except for the K562 cell line) and AML blasts expressing HB-EGF mRNA underwent apoptotic death following exposure to DT, thus demonstrating the presence of the HB-EGF molecule on their membrane. Leukemic cells also released a fully functional HB-EGF molecule that was mitogenic for the Balb/c 3T3 cell line. Factors relevant to the biology of leukemic growth, such as tumor necrosis factor- (TNF-), 1,25-(OH)2D3, and especially all-trans retinoic acid (ATRA), upregulated HB-EGF mRNA in HL-60 or ML-3 cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) induced HB-EGF mRNA and acquisition of sensitivity to DT in one previously HB-EGF–negative leukemia case. Moreover, the U937 and Karpas 299 cell lines expressed HER-4 mRNA. This work shows that HB-EGF is a growth factor produced by primary leukemic cells and regulated by ATRA, 1,25-(OH)2D3, and GM-CSF.

Enhancement and inhibition of cellular responsiveness mediated by the anti-leucocyte monoclonal antibody NDS 71

In this paper we describe the effects of a novel monoclonal antibody (mAb), which either inhibited or enhanced IL-2-stimulated proliferation of human peripheral blood leukocytes (PBL) at the same antibody concentration, under different culture conditions. An effect of this nature on IL-2-stimulated proliferation has not, to our knowledge, previously been described. The mAb NDS 71 bound to more than 98% of both freshly isolated and PHA-stimulated human PBL, with the level of binding markedly up-regulated on activation. An antigen of molecular weight 38-46 kDa was immunoprecipitated. When added to PBL at the beginning of in vitro culture, NDS 71 inhibited IL-2-stimulated proliferation. PHA-stimulated proliferation was enhanced by NDS 71 in identical conditions, demonstrating that the effects of NDS 71 on IL-2-stimulated proliferation were not merely due to non-specific inhibition of cellular proliferation. When NDS 71 was added to IL-2-stimulated PBL 4 h after the start of in vitro culture, proliferation was markedly enhanced, in contrast to the inhibition seen when the same concentration of antibody was added at the start of culture. In summary, NDS 71 markedly affected IL-2-stimulated proliferation, the same concentration of antibody causing either marked inhibition or enhancement, depending on the culture conditions.

Acetaldehyde-serum protein adducts inhibit interleukin-2 secretion in concanavalin A-stimulated murine splenocytes: a potential common pathway for ethanol-induced immunomodulation

Variable immunobiological changes occur with alcohol consumption. Previous studies have shown that acetaldehyde forms stable adducts with serum proteins, including albumin. These adducts are elevated in persons and animals consuming ethanol. We examined the effect of serum protein-acetaldehyde adducts formed with fetal bovine serum (FBS) on concanavalin A-stimulated murine splenocytes. Interleukin-2 (IL-2) secretion and IL-2 receptor (IL-2R) expression were determined as a function of the effect of the acetaldehyde-protein adduct(s). FBS was incubated with acetaldehyde (500, 100, 50, 25, 10, and 0 microM) for 1 hr at 37 degrees C. Excess acetaldehyde was removed by ultrafiltration using a 500 molecular weight cut-off membrane in 3 volumes. Free as well as bound acetaldehyde was quantified using fluorigenic HPLC before and after incubation. Recovered acetaldehyde correlated with the amount added (r2 = 0.996). Splenocytes were cultured for 48 hr in complete medium containing 5% acetaldehyde-treated and 5% untreated FBS with 4 micrograms/ml concanavalin A. Although cell viability was unchanged, acetaldehyde-treated FBS mixed with native FBS decreased IL-2 secretion in a dose-dependent manner. The percentage of cells expressing IL-2R was reduced only at the highest acetaldehyde-FBS dose. Therefore, immunological effects ascribed to ethanol may result in part from the toxic properties of acetaldehyde-protein adducts on IL-2 secretion.

Functional interleukin-2 receptor on a Tac negative human leukaemia T-cell line

Cell line PER-423 was derived from the cells of a patient with an immature acute T-lymphoblastic leukaemia and the growth of this human cell line is strictly dependent on interleukin-2 (IL-2). PER-423 cells express the p75 (beta) subunit of the IL-2 receptor (IL-2R beta), while the p55 chain (IL-2R alpha) is not detectable by immunofluorescence. The analysis of the IL-2R revealed that it is of intermediate affinity and the median effective IL-2 concentration for PER-423 cells (EC50 value) was determined to be 1.44 +/- 0.29 nM. Chemical crosslinking studies showed that the receptor consists of one polypeptide of approximately 95 kDa as well as a doublet of 70 kDa and 60 kDa and does not include the IL-2R alpha-chain. The steady-state mRNA level for the p75 subunit was similar to that present in a cell line expressing an IL-2R alpha+ beta+, while only traces for the alpha-chain were detectable. PER-423 cells can be induced to express the alpha-chain of the IL-2R on the cell surface, concomitant with a much reduced EC50 level. Since cell line PER-423 is functionally dependent on IL-2, it provides an ideal model for IL-2 signal transduction studies and for investigations focusing on the requirements for ligand binding vs activation.

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)

Pseudo-high affinity interleukin 2 (IL-2) receptor lacks the third component that is essential for functional IL-2 binding and signaling

Functional studies of the interleukin 2 receptor (IL-2R) of two (ED515-D and Kit225) IL-2-dependent and three (ED515-I, 3T3-alpha beta 11, and Hut102) IL-2-independent cell lines were done. All of these cell lines appeared to express high as well as low affinity IL-2R. However, ED515-I and 3T3-alpha beta 11, which expressed the IL-2R beta chain, did not bind IL-2 at all when IL-2 binding to their IL-2R alpha chain was blocked with anti-Tac monoclonal antibody, whereas the intermediate affinity binding in ED515-D, Kit225, and Hut102 cells remained. We tentatively called the high affinity IL-2R of the former cells pseudo-high affinity IL-2R. The dissociation constant of pseudo-high affinity IL-2R was higher than that of ordinary high affinity IL-2R. Internalization of cell-bound 125I-IL-2 into ED515-I and 3T3-alpha beta 11 cells was less efficient than that into ED515-D cells. The addition of IL-2 neither promoted cell growth nor upregulated IL-2R alpha chain expression in ED515-I and 3T3-alpha beta 11 cells. Furthermore, tyrosine phosphorylation of the cellular proteins (p120, p98, p96, p54, and p38) was induced or enhanced in response to the addition of IL-2 in ED515-D and Kit225 cells, but not in the cell lines expressing pseudo-high affinity IL-2R. Finally, 125I-IL-2 crosslinking followed by SDS-PAGE analysis showed an 80-kD band corresponding to p65 + IL-2, in addition to bands corresponding to IL-2R alpha and beta chain + IL-2 in cells bearing ordinary high affinity IL-2R but not in cells with pseudo-high affinity IL-2R. Taken together, we consider that another protein whose molecular mass is approximately 65 kD is functionally important in IL-2 binding and subsequent signal transduction and may be the third component of IL-2R.

The third molecule associated with interleukin 2 receptor alpha and beta chain

It is known that the affinity cross-linking study of the human high-affinity Interleukin 2 (IL-2) receptor reveals triplet bands consisting of 70 kDa alpha chain(Tac)-IL-2 and the 90/80 kDa doublet. We found the cell lines lacking the lower band of the doublet in spite of the expression of both alpha and beta chains. No IL-2 binding was detectable in the presence of anti-Tac antibody in these cells. Immunoprecipitation from the cell extract of [125 I] IL-2-cross-linked T cells with anti-beta chain polyclonal IgG detected the upper band, but not lower band of the doublet. These data suggest that the lower band of the doublet represents an unknown IL-2-binding protein (p65) distinct from the beta chain and this molecule may be involved in the intermediate-affinity IL-2 binding together with the beta chain.

Cytometrically detected specific binding of interleukin 2 to cells

We have developed a new technique for detecting binding of interleukin 2 (IL-2) to cells. This technique involves incubating the cells with IL-2 and then analysing the cell surface with specific anti-IL-2 antibodies and flow cytometry. This binding was only detected on tumor cells that possessed the p55 subunit of the IL-2 receptor. The role of p55 was ascertained by inhibition of the binding with a monoclonal antibody to p55. Although p55 is necessary for cytometrically detected IL-2 binding, further studies demonstrated that p55 is not sufficient. Thus, cytometrically-detected binding is likely to involved the contribution of other IL-2 surface receptors. Interleukin-2 binding to peripheral blood T lymphocytes and to a non-transformed T-cell clone was also detected cytometrically and it was shown that this binding is regulated by the activation status of the cells. Whereas IL-2 binding to quiescent T cells could not be detected, upon activation abundant binding was seen. The functional consequences of this type of cellular binding were studied. Interleukin-2 binding to cells during a short pulse was shown to have significant long-term consequences both for T-cell proliferation and for the enhancement of major histocompatibility complex (MHC)-non-restricted cytotoxicity.

The interleukin-2/interleukin-2 receptor system: structural, immunological, and clinical features

Interleukin-2 (IL-2) has been the first and more extensively studied cytokine, in particular for its central role in the mechanisms of cell growth and differentiation. The function of IL-2 is mediated through specific receptors (IL-2R) present on the membrane of reacting cells. Using hybridoma and recombinant DNA technologies, both IL-2 and IL-2R have been biochemically characterized and purified and are available for in vitro and in vivo studies. The biological and clinical investigations on IL-2/IL-2R system have contributed to opening new avenues for the comprehension of phenomena that are critically important for biology, immunology and medicine.