RESUMEN
BACKGROUND: The growing prevalence of chronic illnesses requires nurses to support self-management and help patients integrate the chronic illness into their life. To our knowledge there are currently no training programs that combine the necessary components to adequately enhance nurses' competencies in self-management support. OBJECTIVE: The systematic development and validation of a need-supportive training in self-management support for nurses. DESIGN: A three-phased study, according to van Meijel et al. (2004), with collection of building blocks, design, and validation of the need-supportive character of the training. SETTING AND PARTICIPANTS: Eight training groups with 30 nurses, 34 nursing students and nine social healthcare workers from different nursing colleges in Flanders, Belgium. METHODS: In phase one a literature review, current practice analysis, and problem and needs analysis were performed. In phase two, the INTENSS training intervention was developed, framed within the Self-Determination Theory and the 5A's-Model. The training consisted of a basic training module and a video-interaction guidance module. The intervention was subsequently tested in eight training groups (N = 73). Participants provided feedback during focus group discussions. The intervention was cyclically adapted to trainees' experiences and suggestions. In phase three, we evaluated the need-supportive character of the training intervention. RESULTS: Phase one indicated the need for training, since nurses' application of self-management support was limited and practiced from a narrow medical point of view. In phase two we developed a theory-driven and multifaceted training, building on attitude, knowledge, skills and reflection in the training. The training was framed within the Self-Determination Theory both at the didactical level as well as on content and format. Overall, participants appreciated the building blocks of the training as supporting their basic needs for autonomy, relatedness and competence. CONCLUSIONS: INTENSS, a multifaceted need-supportive training in self-management support was developed, successfully taking into account participants' needs.
Asunto(s)
Enfermeras y Enfermeros , Automanejo , Estudiantes de Enfermería , Actitud del Personal de Salud , Enfermedad Crónica , HumanosRESUMEN
A model system has been developed to study extrathymic T cell differentiation. Mice have been thymectomized, lethally irradiated, and reconstituted with bone marrow cells depleted of Thy-1-positive cells. After 8 wk, the spleen cells of these 5athymic, bone marrow-reconstituted chimeras contain Thy-1-positive pre-cytolytic T lymphocytes (CTL) that are able to respond to antigen only when exogenous interleukin 2 is added to culture.. The phenotype of these pre-CTL is similar to that of thymocytes, suggesting that they may be an immature T cell. Initial evaluation of the CTL repertoire of these athymic mice demonstrates that the CTL generated to trinitrophenyl-modified syngeneic cells are H-2 restricted and that the CTL generated to alloantigens have many of the cross-reactivities observed in normal but not in nude mice. The discrepancies observed in the CTL repertoire between these thymectomized chimeras and nude mice are discussed.
Asunto(s)
Citotoxicidad Inmunológica , Linfocitos T/inmunología , Animales , Antígenos Ly , Antígenos de Superficie , Trasplante de Médula Ósea , Quimera , Reacciones Cruzadas , Antígenos H-2 , Interleucina-2/farmacología , Complejo Mayor de Histocompatibilidad , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Antígenos Thy-1 , TimectomíaRESUMEN
It was demonstrated previously that the cytolysis of murine viral lymphoma cells by anti-murine sarcoma virus (MSV) syngeneic T-killer lymphocytes was restricted by some products of the H-2 complex. The respective role of the products of different regions of the H-2 complex were studied with six H-2(b) and three H-2(d) lymphomas induced by five different type C viruses. They were tested in a classical chromium release test against anti-MSV T-killer cells obtained from different inbred strains of mice, including several H-2 recombinants. Tumors o pound the H-2(b) haplotype were lysed only when effectors and target cells have in common the D(b) region. On the contrary an identity limited to the K end of the H-2 complex is necessary and sufficient in the H-2(d) haplotype. An in vitro restimulation of the spleen cells with concanavalin A strongly increased the activity of in vivo-primed T lymphocytes but did not provide any response for in vivo-primed but nonresponder cells. Preincubation of the tumor cells with anti-H-2 sera abolished the lysis by syngeneic anti-MSV effector lymphocytes. The same results were obtained by preincubating the H-2(b) targets with anti-H-2D(b), or the H-2(d) target with anti-H-2K(d). Preincubation with anti-H-2K(b) or anti- H-2D(d) were ineffective. These results show that the T-killer/target cells interaction in the MSV system involved some products of the H-2 complex which might be different with the various H-2 haplotypes and could possibly vary according to the antigenic specificity. A specific association of a viral product with a normal cellular structure, directed by the H-2 region during the viral budding could explain the observed results.
Asunto(s)
Antígenos Virales , Gammaretrovirus/inmunología , Antígenos de Histocompatibilidad , Inmunidad Celular , Linfoma/inmunología , Virus del Sarcoma Murino/inmunología , Linfocitos T/inmunología , Animales , Reacciones Antígeno-Anticuerpo , Pruebas Inmunológicas de Citotoxicidad , Genes , Ligamiento Genético , Isoanticuerpos , Ratones , Ratones Endogámicos , Neoplasias Experimentales/inmunología , Bazo/inmunologíaRESUMEN
Abnormal production of erythropoietin (Epo) has been described in several human and murine erythroleukemia. The murine IW32 cell line is derived from an F-MuLV-induced erythroleukemia. An autocrine Epo production due to the rearrangement of one Epo allele has been previously described (Beru et al., 1989). However, the exact mechanism leading to the transcriptional activation of the abnormal Epo gene was unknown. In this study, we show that this deregulated expression results from a deletion within chromosome 5. The Epo gene in the abnormal allele is under the control of the G-protein beta2 subunit gene promoter and the expressed mRNA results from the fusion of the non coding exon 1 of the G-protein beta2 subunit gene to a truncated Epo exon 1 gene. This resulting abnormal cDNA allows the expression of a normal Epo protein.
Asunto(s)
Eritropoyetina/genética , Proteínas de Unión al GTP/genética , Regulación Neoplásica de la Expresión Génica/genética , Reordenamiento Génico , Leucemia Eritroblástica Aguda/genética , Animales , Secuencia de Bases , ADN Complementario , Humanos , Leucemia Eritroblástica Aguda/patología , Ratones , Datos de Secuencia Molecular , Células Tumorales CultivadasRESUMEN
The growth factor interleukin 2 (IL2) binds to high and low-affinity receptors (Kd approximately 10-100 pM and 10 nM, respectively) present on activated T lymphocytes. High-affinity receptors are composed of two non-convalently linked polypeptides, alpha and beta of 55 and 70 kDa. These two polypeptides do not share any sequence homology, but each of them, in the absence of the other, binds IL2: alpha with a Kd approximately 10 nM and beta with a Kd approximately 1 nM. When these two chains are associated in lymphocytes, they form high-affinity receptors that mediate IL2 endocytosis and degradation, and transduce IL2 signaling. On cells that physiologically express IL2 receptors, such as activated T lymphocytes, both high and low affinity-receptors are present simultaneously on the cell surface, and low-affinity receptors (alpha without beta) are, in most instances, more abundant by a factor 5 to 10 than high-affinity receptors (alpha associated to beta). Low-affinity receptors bind IL2 but do not induce its internalization and signaling. The physiological role of the complexity of this receptor system is not fully understood. In the present study, we have investigated directly the fate of the high-affinity receptors when the ligand is endocytosed. By confocal microscopy, using two monoclonal antibodies specific for alpha and for beta, respectively, we show that each of these two polypeptides is located in intracellular endocytic compartments. Therefore, when the alpha chain is part of high-affinity receptors, it is endocytosed, as opposed to when it is part of low-affinity receptors and is not endocytosed.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Receptores de Interleucina-2/metabolismo , Linfocitos T/metabolismo , Brefeldino A , Células Clonales/efectos de los fármacos , Células Clonales/metabolismo , Cicloheximida/farmacología , Ciclopentanos/farmacología , Endocitosis/efectos de los fármacos , Humanos , Interleucina-2/metabolismo , Interleucina-2/farmacología , Peso Molecular , Receptores de Interleucina-2/análisis , Receptores de Interleucina-2/efectos de los fármacos , Linfocitos T/efectos de los fármacos , Células Tumorales CultivadasRESUMEN
Lymphoma cells induced in vivo by exogenous C type viruses are usually used as target cells to test the activity of cytolytic T lymphocytes (CTL) directed against the virus-induced cell surface FMR antigen. Such lymphomas are available only in a small number of inbred strains of mice, thus setting limits to the study of H-2 antigens in the interaction between CTL and tumor target cells. A method is proposed to overcome this, using mitogen-induced blast cells from adult mice neonatally infected with C type viruses. Such blast cells bear serologically detectable viral antigens and function as convenient targets in the chromium release test, as well as competitor cells or stimulator cells in vitro. With this method it has been possible to study T cell-mediated anti-FMR reactions in 12 different inbred strains of mice bearing 10 different H-2 haplotypes. The same method could probably be used in any inbred strain, greatly improving the possibility of immunogenetic studies in C type virus systems.
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Citotoxicidad Inmunológica , Técnicas Inmunológicas , Linfoma/inmunología , Linfocitos T/inmunología , Animales , Transformación Celular Viral , Activación de Linfocitos , Ratones , Ratones Endogámicos BALB C/inmunología , Ratones Endogámicos C57BL/inmunología , Ratones Endogámicos/inmunología , Mitógenos/farmacología , RetroviridaeRESUMEN
We have previously described a human tumor T cell line, IARC 301, which constitutively expresses biologically functional interleukin 2 (IL2) receptors. The fate of IL2 after binding to surface high affinity receptors was investigated. After a few minutes, IL2 is internalized at 37 degrees C and is subsequently degraded and released in the medium. The half-life for surface high affinity IL2 receptors, as measured in the presence of cycloheximide, is about 1 h and does not depend upon the presence of IL2. After trypsin digestion of cell surface high affinity receptors in the absence of protein biosynthesis, we could not detect any receptor reappearance on the cell membrane, whether IL2 was added or not. Taken together these results show that IL2 receptors are constantly internalized in these cells in the presence or absence of IL2 and that they do not recycle to the plasma membrane after receptor-mediated endocytosis.
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Endocitosis , Interleucina-2/fisiología , Receptores Inmunológicos/metabolismo , Linfocitos T/metabolismo , Línea Celular , Membrana Celular/metabolismo , Cicloheximida/farmacología , Semivida , Humanos , Linfoma/metabolismo , Receptores Inmunológicos/efectos de los fármacos , Receptores de Interleucina-2RESUMEN
A model system has been developed to study extrathymic T cell differentiation; mice have been thymectomized, lethally irradiated, and reconstituted with bone marrow cells depleted of Thy-1+ cells. After 8 wk, the spleen cells of these athymic, bone marrow-reconstituted chimeras contain Thy-1+ precytolytic T lymphocytes (CTL) that are able to respond to antigen only if supernatant from Con A-activated T cells is added to culture. The phenotype of these pre-CTL is similar to that of thymocytes, suggesting that they may be immature T cells. Initial evaluation of the CTL repertoire of these athymic mice demonstrated that the CTL generated to trinitrophenyl-modified syngeneic cells are H-2-restricted, and that the CTL generated to alloantigens have many of the cross-reactivities observed in normal mice but not in nude mice. In this report, we demonstrate a helper T cell defect in these thymectomized chimeras. These chimeras lack an Ly-1+ helper cell required for thymocytes to differentiate to CTL. Further studies revealed that when spleen cells from these thymectomized chimeras were stimulated with Con A, they produced normal levels of interleukin 2. However, these splenocytes were defective in the production of another factor needed for CTL differentiation.
Asunto(s)
Linfocinas/biosíntesis , Quimera por Radiación , Células Madre/inmunología , Linfocitos T/inmunología , Animales , Trasplante de Médula Ósea , Diferenciación Celular , Concanavalina A/farmacología , Concanavalina A/fisiología , Interleucina-2/biosíntesis , Activación de Linfocitos , Ratones , Ratones Endogámicos C57BL , Bazo/inmunología , Células Madre/citología , Linfocitos T/citología , Linfocitos T Citotóxicos/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Timectomía , Trinitrobencenos/inmunologíaRESUMEN
The ability of tumor cells to produce and to respond to their own growth factor (autocrine secretion) may be of importance for their growth. We describe a human tumor cell line regulated by an autocrine secretion of the growth factor interleukin 2 (IL-2). This T-lymphocyte cell line, IARC 301, was established from a patient with a T-cell lymphoma in the absence of any added specific growth factor. It constitutively expresses biologically functional high-affinity cell-surface receptors for IL-2 as shown by the binding of both radiolabeled purified IL-2 and monoclonal antibodies to IL-2 receptors. In addition, it synthesizes IL-2, which is bound to cell surface receptors. Monoclonal antibodies directed against either IL-2 or the IL-2 receptor block IARC 301 cell growth. These findings demonstrate that the proliferation of this tumor cell line is mediated by an autocrine pathway involving endogenous IL-2 production and its binding to cell surface receptors.
Asunto(s)
Interleucina-2/fisiología , Linfoma/patología , Anticuerpos Monoclonales , División Celular/efectos de los fármacos , Línea Celular , Humanos , Interleucina-2/análisis , Cinética , Radioinmunoensayo , Receptores de Antígenos de Linfocitos T/metabolismo , Receptores Inmunológicos/metabolismo , Receptores de Interleucina-2RESUMEN
High-affinity interleukin 2 (IL2) receptors on human T lymphocytes are multimeric complexes containing two IL2-binding polypeptides, alpha and beta chains of 50-55 and 70-75 kDa, respectively, associated by noncovalent bonds. IL2 binds to high-affinity IL2 receptors on the surface of T lymphocytes, mediates cell growth, and is internalized. In this paper, we used a biochemical method to directly identify the receptors components internalized together with the ligand. 125I-IL2-receptor complexes were solubilized with the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate, and IL2-binding polypeptides were identified by cross-linking with disuccinimidyl suberate. Under such conditions, the noncovalent association between alpha and beta is maintained. After IL2 internalization, two complexes of about 70 and 90 kDa, IL2 crosslinked to alpha and beta, respectively, were found inside the cells. Both components were immunoprecipitated with either anti-alpha or anti-beta monoclonal antibodies. This shows that the alpha and beta chains are found in an intracellular compartment after IL2 endocytosis, and remain associated as a ternary complex with IL2.
Asunto(s)
Endocitosis , Interleucina-2/metabolismo , Receptores de Interleucina-2/metabolismo , Ácidos Cólicos , Reactivos de Enlaces Cruzados , Detergentes , Electroforesis en Gel de Poliacrilamida , Humanos , Radioisótopos de Yodo , Cinética , Succinimidas/química , Células Tumorales CultivadasRESUMEN
The T lymphocyte growth factor interleukin 2 binds to surface high-affinity receptors and is rapidly internalized and degraded in acidic organelles. The alpha and beta chains of high-affinity interleukin 2 receptors are internalized together with interleukin 2. To identify the intracellular pathway followed by interleukin 2, we have compared the subcellular distribution of interleukin 2, transferrin and a fluid-phase marker, horseradish peroxidase, in the human T cell line IARC 301.5. Transferrin was used as a marker of early and recycling endosomes, and horseradish peroxidase to probe for the whole endocytic pathway. Fractionation of intracellular organelles on a discontinuous sucrose gradient showed that internalized interleukin 2 is initially mostly found in compartments with similar densities to transferrin, e.g. early and recycling endosomes. The kinetics of entry and exit of interleukin 2 from such organelles was much slower than that of transferrin. Later on, interleukin 2 is predominantly found in dense lysosome-containing fractions. Very little, if any, interleukin 2 was found in fractions corresponding to late endosomes containing horseradish peroxidase. These results suggest that, after endocytosis, interleukin 2 enters early or recycling endosomes before it reaches dense lysosomes.
Asunto(s)
Interleucina-2/metabolismo , Linfocitos T/metabolismo , Transferrina/metabolismo , Biomarcadores , Compartimento Celular , Línea Celular , Endosomas/metabolismo , Peroxidasa de Rábano Silvestre/farmacocinética , Humanos , Cinética , Lisosomas/metabolismo , Sondas Moleculares , Fracciones Subcelulares/metabolismoRESUMEN
The effect of cyclosporin A (CsA), a potent immunosuppressive agent, on a human T-cell line, IARC 301, which constitutively secretes interleukin-2 (IL-2) and expresses high-affinity IL-2 receptors, was investigated. We show that CsA inhibits IARC 301 cell growth. CsA also prevents the constitutive secretion of IL-2 in this T-cell line by blocking transcription of the IL-2 gene. If exogenous IL-2 is added together with CsA for 3 days, the cells grow as well as untreated controls. Thus, under such conditions, CsA inhibits IARC 301 growth by preventing its endogenous constitutive IL-2 synthesis. This demonstrates that IL-2 stimulates the proliferation of this cell line by an autocrine pathway, in agreement with our previous data. We also show for the first time, that CsA not only can inhibit IL-2 production of T cells upon activation, but that it can also prevent ongoing constitutive IL-2 synthesis of a T-cell line. Autocrine growth stimulation of tumor cells by cytokines has been demonstrated in a few cases. CsA inhibits synthesis of several cytokines. Probing for the autocrine growth of tumor cells by studying the effect of CsA and its reversibility by cytokines on their proliferation may be simple and useful.
Asunto(s)
Ciclosporinas/farmacología , Linfocitos T/efectos de los fármacos , División Celular/efectos de los fármacos , Línea Celular , Humanos , Interleucina-2/genética , Interleucina-2/metabolismo , Interleucina-2/farmacología , ARN Mensajero/análisis , Receptores Inmunológicos/análisis , Receptores de Interleucina-2 , Linfocitos T/metabolismoRESUMEN
We have described a human tumor T cell line, IARC 301, which constitutively expresses high affinity interleukin 2 (IL2) receptors, and showed that after binding to its receptors, IL2 is endocytosed and degraded. Here we present evidence that IL2 down-regulates its own high affinity receptors. Within 1 h, IL2 induces a 60% decrease in surface receptor expression. In order to maintain this down-regulation, IL2 concentration must be high enough for the receptors to be saturated throughout the incubation. The effect of IL2 on the kinetics of receptor internalization was investigated with two approaches. First, the initial rate of IL2 internalization was measured, and no difference could be detected whether the receptors were saturated with IL2 or only partially occupied. Second, the initial rate of surface receptor decay was followed and found to be significantly decreased in the presence of IL2. Although the half-life of IL2 receptors is very short in the absence of IL2, t 1/2 approximately 65 min, suggesting that these receptors are constantly endocytosed, it can still be reduced to t 1/2 approximately 25 min when the receptors are saturated with ligand. This suggests that occupied receptors are internalized faster than and independently from free receptors. The difference in internalization rates can explain the observed receptor down-regulation.
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Interleucina-2/farmacología , Linfoma/metabolismo , Receptores Inmunológicos/metabolismo , Algoritmos , Línea Celular , Semivida , Humanos , Receptores de Interleucina-2 , Linfocitos TRESUMEN
The cytolyse of lymphoma cells by anti-MSV-CTL requires an H-2 identity on CTL and target cells. It can be limited to D or K antigens. An altered cells hypothesis is the more likely hypothesis in H-2a or H-2d tumour cells. However the D antigen alone is involved in H-2b tumours Arguments are given which supports the existence of Ir genes controlling the formation of CTL against H-2Dd modified by MSV.
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Antígenos de Histocompatibilidad , Linfoma/inmunología , Virus de la Leucemia Murina de Moloney , Linfocitos T/inmunología , Animales , Efecto Citopatogénico Viral , Pruebas Inmunológicas de Citotoxicidad , RatonesRESUMEN
Cytolytic T lymphocytes (CTL) from murine sarcoma virus (MSV) or Friend leukaemia virus (FLV) inoculated mice lyse syngeneic much more efficiently than allogeneic FMRGi+ lymphoma cells. By comparing the cytolysis of various H-2 different 51Cr lymphomas by CTL from several inbred and congenic lines differing at H-2, and by competition experiments using unlabelled cells, one can demonstrate that this phenomenon is due to an H-2 barrier. H-2b/H-2d hybrid-anti-MSV-CTL immunized by H-2b, H-2d or H-2b/H-2d tumours lyse only FMRGi+ lymphomas of the same H-2, and their activity for a given target is inhibited only by H-2-identical competitive cells. H-2 antigens are therefore directly involved in the interaction between tumour cells and immune CTL which probably react with an 'H-2 modified' antigen of the tumour cells surface. The use of CTL from intra-H-2 recombinant lines shows that H-2D and probably H-2K molecules are involved, but vary according to the tumour cells. A possible role of the I region is discussed as well as the implications of these results in immunosurveillance against viral neoplasia.
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Antígenos de Neoplasias , Antígenos Virales , Antígenos de Histocompatibilidad , Leucemia Experimental/inmunología , Sarcoma Experimental/inmunología , Infecciones Tumorales por Virus/inmunología , Animales , Pruebas Inmunológicas de Citotoxicidad , Virus de la Leucemia Murina de Friend/inmunología , Inmunidad Celular , Técnicas In Vitro , Virus de la Leucemia Murina/inmunología , Ratones , Ratones Endogámicos , Virus de la Leucemia Murina de Moloney/inmunología , Virus Rauscher/inmunología , Virus del Sarcoma Murino/inmunología , Linfocitos T/inmunologíaRESUMEN
Membranes and solubilized, reconstituted membranes from Moloney-infected tumors MBL-2 have been used to stimulate in vitro secondary cytolytic T lymphocytes (CTL) in C57BL/6 mice primed and Moloney murine sarcoma virus. Membranes are shown to stimulate the generation of Moloney-specific and H-2 restricted CTL. Stimulation with solubilized, reconstituted membranes required the presence of rat lymphocyte Con A supernatant (containing interleukin 2) during the culture. Reconstituted membranes made in the presence of the detergent-insoluble fraction from the plasma membrane were able to stimulate a response in the absence of Con A supernatant.
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Sarcoma Experimental/inmunología , Linfocitos T Citotóxicos/inmunología , Animales , Membrana Celular/inmunología , Transformación Celular Viral , Femenino , Memoria Inmunológica , Interleucina-2/inmunología , Ratones , Virus de la Leucemia Murina de Moloney , SolubilidadRESUMEN
In two different murine systems it is shown that immune response genes, mapping to the D region of the major histocompatibility complex, control the level of the immune response mediated by cytolytic T lymphocytes and specific for the virus induced FMR antigens. The high responder phenotype is dominant. It is associated with the choice of certain H-2 antigens as restricting factors of the T lymphocyte activity, histocompatibility antigens behaving like Ir gene products.
Asunto(s)
Genes MHC Clase II , Antígenos H-2/inmunología , Células Asesinas Naturales/inmunología , Animales , Antígenos H-2/genética , Inmunidad Celular , Ratones , Virosis/inmunologíaRESUMEN
The generation of cytolytic T lymphocytes (CTL) during the immune response directed against the syngeneic X-ray-induced BALB/c RLmale 1 leukemia has been described previously: T killer cells react with a tumor antigen of RLmale 1 cells, and the H-2Dd molecules of the target cells play some role in the interaction. The study of anti-RLmale 1 responses of [(C57BL/6 x BALB/c) x BALB/c] mice shows that the major histocompatibility complex controls the anti-RLmale 1 CTL reaction at a second level, through an Ir gene, with dominant responsiveness, probably mapping to the right of I-B and controlling the high or low-CTL responder phenotype. Another non-H-2 associated gene interferes with the H-2 linked Ir gene, a responder allele at the non-H-2 locus, being necessary for the expression of the high-responder phenotype at the Ir gene locus.
Asunto(s)
Genes MHC Clase II , Antígenos H-2 , Inmunidad Celular , Leucemia Experimental/inmunología , Linfocitos T/inmunología , Animales , Cruzamientos Genéticos , Citotoxicidad Inmunológica , Femenino , Ligamiento Genético , Hibridación Genética , Masculino , Ratones , Ratones Endogámicos AKR , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , Ratones Endogámicos C57BLRESUMEN
In the present report, we further explored the mechanisms by which 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (paf-acether), a phospholipid mediator of inflammation inhibited PHA-induced CD4+ cell proliferation. Evidence was obtained that CD4+ cells stimulated with either PHA or immobilized OKT3 in the presence of paf at concentrations that block CD4+ cell proliferation, exhibited a marked decrease in high affinity IL-2R expression. Importantly, paf did not prevent the binding of IL-2 to its receptor. Scatchard analysis of the binding data indicated that paf caused more than 50% decrease in the number of IL-2 high affinity sites per cell, whereas the receptor ligand affinity remained essentially constant. Moreover, the down-regulation of high affinity IL-2R was also accompanied by a loss of IL-2-dependent proliferative capacity. Together these data suggest that decreased expression of high affinity IL-2R may contribute to the diminished proliferative activity observed in CD4+ cells stimulated with PHA or immobilized OKT3 in the presence of paf. They further emphasize the potential role of lipid proinflammatory mediators such as paf in the regulation of T cell activation.