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A Bárcena

Publications and source records attributed to A Bárcena.

At least 19 recordsLinked to original sources
PubMed2001

Broad distribution of colony-forming cells with erythroid, myeloid, dendritic cell, and NK cell potential among CD34(++) fetal liver cells.

The generation of erythroid, myeloid, and lymphoid cells from human fetal liver progenitors was studied in colony-forming cell (CFC) assays. CD38(-) and CD38(+) progenitors that expressed high levels of CD34 were grown in serum-deprived medium supplemented with kit ligand, flk2/flt3 ligand, GM-CSF, c-mpl ligand, erythropoietin, and IL-15. The resulting colonies were individually analyzed by flow cytometry. CD56(+) NK cells were detected in 21.9 and 9.9% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. NK cells were detected in mostly large CD14(+)/CD15(+) myeloid colonies that also, in some cases, contained red cells. NK cells were rarely detected in erythroid colonies, suggesting an early split between the erythroid and the NK cell lineages. CD1a(+) dendritic cells were also present in three-quarters of the colonies grown from CD38(-) and CD38(+) progenitors. Multilineage colonies containing erythrocytes, myeloid cells, and NK cells were present in 13.7 and 2.7% of colonies grown from CD38(-) and CD38(+) progenitors, respectively. High proliferative-potential CFCs that generated multilineage colonies were also detected among both populations of progenitors. The total number of high proliferative-potential CFCs with erythroid, myeloid, and NK cell potential was estimated to be 2-fold higher in the CD38(+) fraction compared with the CD38(-) fraction because of the higher frequency of CD38(+) cells among CD34(++) cells. The broad distribution of multipotent CFCs among CD38(-) and CD38(+) progenitors suggests that the segregation of the erythroid, myeloid, and lymphoid lineages may not always be an early event in hemopoiesis. Alternatively, some stem cells may be present among CD38(+) cells.

ADP-ribosyl Cyclase↗
PubMed2001

[Geriatric management of the frail elderly with hip fracture may improve their clinical outcome].

BACKGROUND: The treatment of osteoporotic hip fracture requires the intervention of different medical specialties. The purpose of this study was to know the clinical profile of patients with an acute hip fracture referred for assessment and management to a geriatric assessment team (GAT) and the influence of this kind of geriatric care in their hospital outcome. PATIENTS AND METHOD: All patients 65 year-old or older admitted in a teaching hospital for a hip fracture in a 12 month period were included. The clinical, functional, cognitive and social status were assessed at admission and at discharge in both groups: the patients managed by the GAT and the patients that were not. The patients' characteristics of both groups were compared, and a multivariant analysis was applied to search the variables independently associated wit a better clinical course. RESULTS: On admission, the GAT patients (n = 202) were significantly (p < 0.05) older (84.4 vs 81.7 years), had more previous functional impairment (Barthel index 72 vs 79), more previous diseases (5.4 vs 3.3) and medications (3.2 vs 1.9), presented more frequency of cognitive impairment (52 vs 41%), of high surgical risk (54 vs 26%) and more need of social assistance at home (57 vs 38%) than non-referred patients (n = 200). At discharge, GAT patients had better functional status (Barthel index 38.5 vs 34), had been surgically treated (92 vs 84%), had received physiotherapy (83.7 vs 66.5%) and walked more (56.1% vs 33.8%) than others. In the multivariant analysis, the GAT intervention shows like an independent variable associated to higher frequency of surgical treatment (OR 4.21; CI, 2.80-6.34), to recovery of walking ability (OR, 8.26; CI, 5.23-13.04) and to receive more medical diagnosis (OR, 79.69; CI: 55.48-114.45). The GAT intervention was not associated to a longer hospital stay. CONCLUSIONS: The patients with hip fracture in acute phase required for management by a GAT are more complex than those who were not consulted. In these patients GAT intervention improve their clinical outcome and the efficiency of hospital admission.

Aged↗
PubMed2001

Further experience of nonagenarians with hip fractures.

Our purpose was to investigate the factors after predictive outcome 3 months after the injury in terms of mortality and effective independent walking of nonagenarians with hip fracture. A prospective study was carried out for 2 yr in the orthopaedic wards on patients referred to geriatricians. The data were subjected to logistic regression forward stepwise analysis. Eighty-nine patients were included in the study; 55 (61.8%) had a trochanteric fracture and 86 required a surgical procedure. Before the fracture, 83 patients (93.3%) were able to walk by themselves or with minimal supervision. Forty-three patients (48.3%) had an American Society of Anaesthesiologists' of III-IV score. The mean number of postoperative complications was four. Mean hospital stay was 18.2 days. Within 3 months, 19 patients (21.3%) had died and 58 (69%) were living in their previous residence. Thirty-three (50% of living patients) were able to walk by themselves or with minimal help within 3 months of the fracture. Predictive variables for 3-month mortality were pre-fracture dependence on others for personal toilet and the presence of cognitive impairment. Predictive variables for independent efficient walking were bowel control and absence of cognitive impairment before the fracture, as well as no development of bed sores during hospitalization.These nonagenarian patients with hip fractures show low perioperative mortality, frequently return to their previous accommodation and present a limited recovery of walking ability.

Activities of Daily Living↗
PubMed2001

Transplantation of a fetus with paternal Thy-1(+)CD34(+)cells for chronic granulomatous disease.

A fetus diagnosed with X-linked chronic granulomatous disease was transplanted with Thy-1(+)CD34(+) cells of paternal origin. The transplant was performed at 14 weeks gestation by ultrasound guided injection into the peritoneal cavity. The fetus was delivered at 38 weeks gestation after an otherwise uneventful pregnancy. Umbilical cord blood was collected and used to determine the level of peripheral blood chimerism as well as levels of functional engrafted cells. Flow cytometry was used to detect donor leukocytes identified as HLA-A2(-)B7(+) cells, whereas recipient cells were identified as HLA-A2(+)B7(-) cells. No evidence of donor cell engraftment above a level of 0.01% was found. PCR was used to detect HLA-DRB1*15(+) donor cells among the recipient's HLA-DRB1*15(-) cells, but no engraftment was seen with a sensitivity of 1:1000. The presence of functional, donor-derived neutrophils was assessed by flow cytometry using two different fluorescent dyes that measure reactive oxygen species generated by the phagocyte NADPH oxidase. No evidence of paternal-derived functional neutrophils above a level of 0.15% was observed. Peripheral blood and bone marrow samples were collected at 6 months of age. Neither sample showed engraftment by HLA typing using both flow cytometry and PCR. Functional phagocytes were also not observed. Furthermore, no indication of immunological tolerance specific for the donor cells was indicated by a mixed lymphocyte reaction assay performed at 6 months of age. While there appears to be no engraftment of the donor stem cells, the transplant caused no harm to the fetus and the child was healthy at 6 months of age. Analyses of fetal tissues, obtained from elective abortions, revealed that CD3(+) T cells and CD56(+)CD3(-) NK cells are present in the liver at 8 weeks gestation and in the blood by 9 weeks gestation. The presence of these lymphocytes may contribute to the lack of donor cell engraftment in the human fetus.

Adult↗
PubMed2000

Differential effects of interleukin-3, interleukin-7, interleukin 15, and granulocyte-macrophage colony-stimulating factor in the generation of natural killer and B cells from primitive human fetal liver progenitors.

The regulatory roles of a number of early-acting growth factors on the generation of natural killer (NK) cells and B cells from primitive progenitors were studied. Experiments focused on the contributions of granulocyte-macrophage colony-stimulates factor (GM-CSF) and interleukin-3 (IL-3) to the regulation of the early events of lymphopoiesis.Two progenitor populations isolated from human fetal liver were studied, CD38(-)CD34(++)lineage(-) (Lin(-)) cells (candidate hematopoietic stem cells [HSCs]) and the more mature CD38(+)CD34(++)Lin(-) cells. The effects of different cytokines on the generation of CD56(+)CD3(-) NK cells and CD19(+) B cells were studied in serum-deprived cultures in the absence of stroma.NK cells generated in vitro were able to kill NK-sensitive target cells, expressed NK-associated marker CD161 (NKR-P1A), but exhibited little or no expression of CD2, CD8, CD16, CD94/NKG2A, or killer cell inhibitory receptors (KIRs). Among the cytokine combinations tested, kit ligand (KL) and IL-15 provided the best conditions for generating CD56(+) NK cells from CD38(+)CD34(++)Lin(-) cells. However, either flk-2/flt3 ligand (FL), GM-CSF, IL-3, or IL-7 could partially substitute KL. All of these cytokines also supported the growth of NK-cell progenitors from candidate HSC, with the combination of IL-15, KL, GM-CSF, and FL generating the greatest number of CD56(+) cells. B cells were generated from both progenitor populations in response to the combined effects of KL, FL, and IL-7. Both B and NK cells were generated with the further addition of IL-15 to these cultures. The in vitro generated B cells were CD10(+), CD19(+), HLA-DR(+), HLA-DQ(+), and some were CD20(+), but no cytoplasmic or surface immunoglobulin M expression was observed. In contrast with NK lymphopoiesis, GM-CSF, IL-3, and IL-15 had no effect on the generation of B cells from CD38(-)CD34(++)Lin(-) cells, and GM-CSF inhibited B-cell generation from CD38(+)CD34(++)Lin(-) progenitors. These findings indicate a differential regulation of NK and B lymphopoiesis beginning in the early stages of hematopoiesis as exemplified by the distinctive roles of IL-7, IL-15, GM-CSF, and IL-3.

ADP-ribosyl Cyclase↗
PubMed2000

Fetal bone marrow as a source of stem cells for in utero or postnatal transplantation.

We examined the potential of human fetal bone marrow (FBM) as a source of haematopoietic stem cells for transplantation. The median number of cells obtained between 20 and 24 weeks' gestation was 1.9 x 109 and a median 1.17 x 108 of these cells expressed CD34. Flow cytometry was also used to estimate the content of three different candidate stem cell populations in the tissues older than 20 weeks' gestation. A median 8.8 x 105 CD34++CD38- cells, 1.37 x 106 CD34++CD4+ cells and 2.20 x 106 CD34++CD90+ cells were detected. The content of colony-forming units culture (CFU-C) in the FBM ranged from 2.8 x 104 to 6.0 x 106 per fetus. The CFU-C content could be expanded 50-fold by culture for 1 week in serum-deprived medium and the growth factors kit ligand and granulocyte-macrophage colony-stimulating factor. Positive selection of FBM CD34+/++ cells was achieved using the Baxter Isolex 50 device. An average purity of 82% and yield of up to 19% of CD34+/++ cells was achieved. T cells were depleted by 99.84%. Analysis of candidate stem cell populations and primitive CFU-C suggested a preferential enrichment of these cells over the total population of CD34+/++ cells. All FBM samples were found to be free of microbial contamination at the time of harvest and after selection of CD34+/++ cells. Thus, FBM is a safe source of stem cells. The large number of progenitors and candidate stem cells that can be obtained from FBM makes it suitable for in utero and possibly postnatal transplantation.

Antigens, CD34↗
PubMed1999

Role of CD95/Fas and its ligand in the regulation of the growth of human CD34(++)CD38(-) fetal liver cells.

The functional significance of CD95/Fas expressed by candidate hematopoietic stem cells (HSCs) from human fetal liver was studied by testing the effect of agonistic anti-CD95 monoclonal antibody (mAb) CH-11 and soluble CD95 ligand (sCD95L) on the growth of CD34(++)CD38(-)lineage cells in vitro. Candidate fetal HSCs exhibited a dose-dependent proliferative response to CH-11 as well as to sCD95L when combined with kit ligand (KL) + interleukin 3 (IL-3) under serum-deprived culture conditions. CH-11 mAb increased, in a synergistic fashion, the number of myeloid colony-forming unit culture (CFU-C) generated by candidate HSCs in liquid cultures with the cytokine combinations KL + IL-3, KL + granulocytemacrophage colony-stimulating factor, and KL + IL-6. CH-11 mAb and sCD95L also enhanced erythropoiesis supported by KL + IL-3 + erythropoietin (Epo). Furthermore, sCD95L was able to increase the number of megakaryocytes, granulocytes, and CD34- cells generated in the presence of KL + IL-3 + Epo + thrombopoietin. An analysis performed using Western blotting revealed that the membrane-bound CD95L (mCD95L) was expressed by both immature (total CD34+/++) and mature (CD34-) hematopoietic lin(-) FL cells. Among the CD34(++)lin(-)cells, both the freshly isolated CD38+ and CD38 subsets as well as CD95+ and CD95- cells constitutively expressed mCD95L, demonstrating that the CD95/CD95L system represents a paracrine and potentially autocrine regulator of early hematopoiesis. To study the role of the endogenously produced CD95L, we determined the effects of a neutralizing anti-CD95L NOK-1 on the growth of candidate HSCs. By blocking the endogenous CD95L with NOK-1 mAb, we observed an increase in CFU-C generated by candidate HSCs. We conclude that the endogenous CD95L has an inhibitory effect on fetal candidate HSCs, which can be blocked by sCD95L and CH-11 mAb.

ADP-ribosyl Cyclase↗
PubMed1999

Mid-trimester fetal livers are a rich source of CD34+/++ cells for transplantation.

Human fetal livers (FL), between 16 and 24 weeks of gestation, were studied for their potential as a source of hematopoietic stem cells for prenatal and postnatal transplantation. In this report we give a quantitative evaluation of human FL as a source of candidate stem cells, and develop a protocol for the isolation of these cells free of microbial contaminants and almost free of mature T cells. Human FLs contained a median 1.9 x 10(9) viable cells and a mean of 1.3 x 10(8) CD34+/++ cells (range 1.1 x 10(7) to 4.7 x 10(8)). Regardless of gestational age, no significant differences were apparent in the numbers of total progenitors or in the numbers of candidate stem cells (CD34++ CD38- and CD34++CD4+), suggesting that the expansion in the liver of the early compartments of hematopoietic progenitors reaches a plateau after the sixteenth week of gestation. Colony-forming units culture (CFU-C) were found to range from 4.1 x 10(6) to 2.5 x 10(7) per FL. Positive selection of FL CD34++ cells was achieved using the Baxter Isolex 50 device. An average purity of 74% and yield of 29% of CD34+/++ cells was achieved. T cells were depleted by 99.95%, resulting in a mean of 6.5 x 10(3) T cells per processed liver. Analysis of candidate stem cell populations and primitive colony-forming cells (CFC) suggested a preferential enrichment of these cells over the total population of CD34+/++ cells. Processed CD34+/++cells were found to be sterile. In conclusion, purification of FL progenitors between 16 and 24 weeks of gestation results in a large number of early progenitors suitable for in utero and possibly post-natal transplantation.

Antigens, CD34↗
PubMed1999

Factors predictive of outcome on admission to an acute geriatric ward.

AIM: To investigate which factors predict outcome of elderly patients on discharge and at 6 months. METHODS: A prospective study in an acute geriatric ward. Within 48 h of admission, patients were assessed for social factors, geriatric problems, admission diagnoses, medication, function and mental ability. Outcome measures were mortality, length of stay, institutionalization, readmissions and attendance at accident and emergency within 6 months. RESULTS: 353 patients were studied, with a mean age of 81.8 years. Logistic regression analyses showed that variables predicting hospital mortality were Barthel index on admission, pre-morbid disability and polypharmacy. The only variable independently predictive of prolonged stay in hospital was a Barthel score of <45 on admission. Functional disability on admission was predictive of institutionalization on discharge. Variables predicting mortality within 6 months of discharge were Barthel index on admission <65, presence of pressure sores, malnutrition and polypharmacy. Variables independently predictive of institutionalization were mental state and a low pension. Those who took more than five drugs on admission were more likely to attend accident and emergency and be readmitted. CONCLUSION: Limited activities of daily living and geriatric problems on admission are the strongest predictive factors of outcome, independent of diagnoses.

Aged↗
PubMed1997

Idiopathic normal pressure hydrocephalus: analysis of factors related to cerebrospinal fluid dynamics determining functional prognosis.

This investigation has been undertaken to analyze the findings with both the cerebrospinal fluid (CSF) pressure (Pcsf) and CSF pulse pressure (PP) in order to predict the outcome of patients with the syndrome of idiopathic normal pressure hydrocephalus (NPH). Accordingly, a prospective clinical study was planned in which two groups of patients with NPH, having analogous prevalence of several matched clinical and radiological parameters, were separated on the basis of their positive or negative response to shunting. Both the resting Pcsf and CSF PP profiles were compared in these two groups, and between them and normal controls. CSF PP amplitude and CSF PP latency correlated directly in conditions associated with either normal or high compliance (controls and patients with Alzheimer-like disorders), whereas this correlation was inverse in states of low compliance (NPH). On the other hand, shunt-responders showed a resting Pcsf significantly higher than both non-responders and controls. The following conclusions were obtained: 1) CSF PP is a high-amplitude and relative low-latency wave in NPH when compared with controls: 2) CSF PP amplitude and latency correlate directly in normal subjects and in those with primary cerebral atrophy; 3) a non-reversible stage of NPH could be conceived in contradistinction to the reversible one, in both of which an inverse correlation between the amplitude and the latency takes place, the main difference between them being the resting Pcsf, which is significantly lower in the former than in the latter, depending on the degree of atrophic changes developed.

Adult↗
PubMed1996

Expression of Fas/CD95 and Bcl-2 by primitive hematopoietic progenitors freshly isolated from human fetal liver.

The cell-surface expression and the functional status of the CD95/Fas antigen on primitive hematopoietic progenitors (PHPs) freshly isolated from human fetal liver (FL) were studied. PHPs were phenotypically defined as CD34++ CD38 -/+ cells. The most immature subfractions of PHPs, CD34++CD38- and CD34+2CD38+ FL cells, expressed CD95, whereas the more mature CD34++CD38++ and CD34+CD38++2 FL cells displayed low CD95 expression. Combinations of cytokines, such as kit ligand (KL) + interleukin-3 or KL + granulocyte-macrophage colony-stimulating factor (GM-CSF) upregulated the expression of CD95 on PHPs upon in vitro culture. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) further increased the CD95 expression induced by KL+GM-CSF. The hematopoietic potential of sorted CD34++lineage (lin)- CD95+ versus CD34++ lin-CD95-FL cells was compared by colony-forming unit-culture (CFU-C) assays performed in serum-deprived medium. Lin+ cells were composed of erythrocytes, monocytes, T cells, B cells, and natural killer cells. Our results indicated that both CD95- and CD95+ subsets contained pluripotent progenitors, generating myeloid and erythroid progenitors. The functional status of CD95 and the effects of TNF-alpha and IFN-gamma, cytokines known to induce CD95-mediated apoptosis, were analyzed by incubation of PHPs in the presence of anti-CD95 monoclonal antibodies (MoAbs). The effect of anti-CD95 MoAbs was measured by viable cell counting, flow cytometry, and CFU-C assays. A decrease of CFU-C numbers was observed in the presence of anti-CD95 MoAbs and TNF-alpha and/or IFN-gamma. However, whereas growth factor deprivation induced apoptosis of PHPs, cross-linking of CD95 did not lead to apoptosis of PHPs measured by flow cytometry and viable cell counting. The correlation of increased intracytoplasmic levels of bcl-2 with high levels of cell-surface CD34 and the presence of CD95 on fresh FL cells suggests that bcl-2 may be involved in protecting against CD95-mediated apoptosis of FL PHPs.

Antibodies, Monoclonal↗
PubMed1995

Tracing the expression of CD7 and other antigens during T- and myeloid-cell differentiation in the human fetal liver and thymus.

During the last decade, the function/s of the cell membrane CD7 antigen have been investigated in human mature T and NK cells, showing the direct involvement of this molecule in multiple effector functions related with activation, proliferation, production of cytokines and modification of adhesion properties. The CD7 glycoprotein is not only expressed by mature lymphoid cells, but also by early hematopoietic progenitors and several types of leukemias, suggesting a role of CD7 during hematopoiesis. However, the function of CD7 in the early stages of hematopoietic development has not yet been elucidated. CD7 has been classically considered the earliest T-cell specific marker. This assumption was based on data indicating the presence of CD45+CD7+CD3-CD4-CD8- cells in the human embryonic/fetal liver at the gestational age at which the thymic rudiment is colonized by T-cell progenitors. In the present article, we review recent results obtained by several groups concerning the expression of CD7 and various other cell surface antigens by T-, B- and myeloid-cell progenitors generated in the adult bone marrow and fetal liver. In addition, we present an hypothetical model of hematopoiesis in the fetal liver and thymus.

Antigens, CD↗
PubMed1995

[Decrease in isoflurane requirements and of postoperative pain with preanesthetic intrathecal morphine].

OBJECTIVES: 1) To determine whether preanesthetic intrathecal administration of 0.5 mg morphine reduces isoflurane requirements for anesthetic maintenance. 2) To assess the duration of postoperative analgesia and the type and frequency of complications attributable to the procedure. PATIENTS AND METHODS: A series of 45 adults were distributed into 3 groups of 15 patients each based on site of surgery and site of preanesthetic (30 min) injection of 0.5 mg pure morphine. Control group (C0) patients underwent lumbar surgery and received subcutaneous morphine. Group C0.5 patients also underwent lumbar surgery but received intrathecal morphine. Group A0.5 patients underwent long-duration high abdominal surgery and received intrathecal morphine. Anesthesia was maintained with nitrous oxide (60%) in oxygen (40%) and a variable concentration of isoflurane. Isoflurane needs were assessed by averaging six consecutive measurements of end-tidal isoflurane pressure (M30FETiso) taken at intervals of 5 min. Postoperative analgesia was evaluated by means of a visual analog scale that was converted to numerical units (VASn). RESULTS: M30FETiso in group C0 (0.8%) was always higher (p < 0.01) than in the other two groups. M30FETiso in group A0.5 was higher (p < 0.01) than in group C0.5 during the first 150 min of surgery. After 180 min, there were no differences in M30FETiso (0.10-0.16%) between the two groups receiving intrathecal morphine. VASn results (mean +/- SD) in the first 4 hours were higher in group C0 (7.33 +/- 0.6) than in group C0.5 (1.13 +/- 0.35) and group A0.5 (1.07 +/- 0.26). The time of morphine-dependent analgesia was shorter (p < 0.01) in group C0 (0.62 +/- 0.38 hours) than in groups C0.5 (30.4 +/- 5.11 hours) and A0.5 (28 +/- 4.34 hours). There were no significant differences between the two groups receiving intrathecal morphine. CONCLUSIONS: Preanesthetic subarachnoid lumbar injection of 0.5 mg of pure morphine reduced early requirements for isoflurane in lumbar surgery (0.14% after 60 min). This reduction was initially less in patients undergoing abdominal surgery (0.44% at 60 min) but was the same after 150 min. Postoperative analgesia was long-term and independent of type or duration of surgery. There was no respiratory depression after surgery and the incidence of postoperative complications was similar in the two groups that received subarachnoid morphine.

Adolescent↗
PubMed1994

Lymphoid and myeloid differentiation of fetal liver CD34+lineage- cells in human thymic organ culture.

In this article, we report that the human fetal thymus contains CD34bright cells (< 0.01% of total thymocytes) with a phenotype that resembles that of multipotent hematopoietic progenitors in the fetal bone marrow. CD34bright thymocytes were CD33-/dull and were negative for CD38, CD2, and CD5 as well as for the lineage markers CD3, CD4, and CD8 (T cells), CD19 and CD20 (B cells), CD56 (NK cells), glycophorin (erythrocytes), and CD14 (monocytes). In addition, total CD34+ lineage negative (lin-) thymocytes contained a low number of primitive myeloid progenitor cells, thus suggesting that the different hematopoietic lineages present in the thymus may be derived from primitive hematopoietic progenitor cells seeding the thymus. To investigate whether the thymus is permissive for the development of non-T cells, human fetal organ culture (FTOC) assays were performed by microinjecting sorted CD34+lin- fetal liver cells into fragments of HLA-mismatched fetal thymus. Sequential phenotypic analysis of the FTOC-derived progeny of CD34+lin- cells indicated that the differentiation into T cells was preceded by a wave of myeloid differentiation into CD14+CD11b+CD4dull cells. Donor-derived B cells (CD19+CD20+) were also generated, which produced immunoglobulins (IgG and IgM) when cultured under appropriate conditions, as well as functional CD56+CD3- NK cells, which efficiently killed K562 target cells in cytotoxicity assays. These results demonstrate that the microinjection of fetal liver hematopoietic progenitors into fetal thymic organ fragments results in multilineage differentiation in vitro.

Antigens, CD↗
PubMed1994

In vivo cytokine expression in the thymus. CD3high human thymocytes are activated and already functionally differentiated in helper and cytotoxic cells.

CD4 and CD8 are expressed on mutually exclusive T cell populations that can recognize peptides bound to class II and class I MHC Ags, respectively. These populations have different functions and are different in their capacity to produce cytokines. In this paper we demonstrate that this functional differentiation occurs at the CD3low- CD3high transitional stage: single positive mature CD4+ thymocytes express IL-2 mRNA in vivo, whereas CD8+ thymocytes primarily express perforin. IL-2, perforin, and IFN-gamma mRNAs were almost absent in CD4+CD8+ CD3low but were clearly detectable in CD4+CD8+ CD3high cells, indicating that these genes are induced at the CD3low- CD3high transitional stage. In contrast, IL-4 mRNA levels were highest in the precursor cells but dropped sharply at the CD3low-CD3high transitional stage. These data are consistent with and link two earlier observations, i.e., that activation occurs at the CD3low-CD3high transition and that functional differentiation in helper and cytotoxic cells is already accomplished in the single positive thymocytes. This activation may reflect positive selection and concomitant functional differentiation into helper and cytotoxic T cells.

Animals↗