Screening for neurocognitive impairment, depression, and anxiety in HIV-infected patients in Western Europe and Canada

CRANIum, a cross-sectional epidemiology study in Western Europe and Canada, was conducted to describe and compare the prevalence of a positive screen for neurocognitive impairment (NCI), depressive symptoms, and anxiety in an HIV-positive population either receiving combination antiretroviral therapy (cART) or who were naive to antiretroviral therapy (ART). HIV-positive patients ≥18 years of age attending a routine medical follow-up visit and able to complete the designated screening tools were eligible for study inclusion. The Brief Neurocognitive Screen was used to assess NCI; depressive and anxiety symptoms were assessed using the Hospital Anxiety and Depression Scale. The evaluable patient population (N = 2863) included 1766 men (61.7%) and 1096 (38.3%) women. A total of 1969 patients were cART-experienced (68.8%), and 894 were ART-naive (31.2%). A positive screen for NCI was found in 41.5% of patients (cART-experienced, 42.5%; ART-naive, 39.4%; p = 0.12). A positive screen for depressive symptoms was found in 15.7% of patients (cART-experienced, 16.8%; ART-naive, 13.3%; p = 0.01), whereas 33.3% of patients screened positive for anxiety (cART-experienced, 33.5%; ART-naive, 32.8%; p = 0.71). A greater percentage of women compared with men screened positive for NCI (51.78% vs. 35.1%; p < 0.0001) and depressive symptoms (17.9% vs. 14.3%; p = 0.01). These data suggest that neurocognitive and mood disorders remain highly prevalent in HIV-infected patients. Regular mental health screening in this population is warranted.

Prevalence of depressive and other central nervous system symptoms in HIV-infected patients treated with HAART in Spain

This study was conducted to assess the prevalence of depressive symptoms, sleep disturbances, and subjective cognitive complaints in patients with HIV receiving highly active antiretroviral therapy. Participants completed the "Center for Epidemiological Studies Depression Scale" (CES-D) and a questionnaire on sleep disturbances and subjective cognitive complaints. Mean age of the 799 participants was 43.7 years and 67% were men. Adjusted prevalence of CES-D was 35.4% (95% confidence interval [CI]: 32.0-38.7), with no significant differences between gender and age groups. Sleep disturbances were more prevalent in older versus younger participants (74.0% [95% CI: 70.4-77.7] versus 63.3% [95% CI: 56.8-69.8]). Cognitive complaints were more prevalent in women (52.3% [95% CI: 46.4-58.2]) when compared with men (48.2% [95% CI: 44.7-51.6]). Hepatitis C virus coinfection was a strong predictor of depressive symptoms. Male gender and detectable viral load were independent risk factors for sleep disturbance. A higher CES-D score was an independent risk factor for sleep disturbance and cognitive complaints.

Use of simple noninvasive biomarkers to predict liver fibrosis in HIV/HCV coinfection in routine clinical practice

BACKGROUND

Simple noninvasive tests to predict fibrosis, as an alternative to liver biopsy (LB), are needed. Of these, the aspartate aminotransferase (AST) to platelet ratio index (APRI) and the Forns index (FI) have been validated in HIV/hepatitis C virus (HCV) coinfection. However, these indexes may have lower diagnostic value in situations other than the circumscribed conditions of validation studies. We therefore examined the value of the APRI and FI in HIV/HCV-coinfected patients for the detection of significant fibrosis in real-life conditions.

PATIENTS AND METHODS

HIV/HCV-coinfected patients who had participated in a multicentre cross-sectional retrospective study were selected if they had undergone an LB within 24 months before the last visit. The predictive accuracy of the APRI and FI was measured using the areas under receiver-operating-characteristic curves (AUROCs). Diagnostic accuracy was determined using the positive (PPV) and negative (NPV) predictive values.

RESULTS

A total of 519 coinfected individuals were included in the study. The AUROC [95% confidence interval (95% CI)] of the APRI was 0.67 (0.66-0.71) and that of the FI was 0.67 (0.62-0.71). The PPV of the APRI was 79% and its NPV was 66%. The PPV of the FI was 74% and its NPV was 64%. LB length was available and was > or =15 mm in 120 individuals. In this group, the PPV of the APRI was 85%, and that of the FI was 81%. Using these indexes, 22% of patients could be spared LB. Applying both models sequentially, 30% of patients could be spared LB.

CONCLUSIONS

In HIV/HCV-coinfected patients, the diagnostic accuracy of the APRI in real-life conditions was similar to that in the validation studies. The FI performed less well. However, combining the two indexes to make decisions on anti-HCV therapy may prevent a significant proportion of patients from having to undergo LB.

Prevalence and impact of body physical changes in HIV patients treated with highly active antiretroviral therapy: results from a study on patient and physician perceptions

Patients infected with HIV treated with highly active antiretroviral therapy (HAART) frequently develop body physical changes (BPC) that have an important psychosocial burden. The purpose of this study was to determine the prevalence of BPC observed by HIV-infected patients and their attending physicians and to assess the impact BPC had on daily life. In this epidemiologic multicenter study, patients with HIV infection and their treating physicians filled out parallel questionnaires about their perceptions of specific BPC and their impact on daily activities. A total of 965 patient-physician questionnaires were collected across 98 health centers. Patient's mean age was 43.7 +/- 8.5 years and 72.6% were men. Adjusted prevalence of perceived BPC by patients and physicians was 55.1% (95% confidence interval [CI]: 52.0-58.1) and 55.2% (95% CI: 52.1-58.2), respectively (p = 1.000). Overall patient-physician agreement concerning perception of BPC was 83% (p < 0.0005). The most common BPC was lipoatrophy, described by 46.8% (95% CI: 43.7-49.8) of patients and 49.4% (95% CI: 46.3-52.5) of physicians (p = 0.033) followed by lipohypertrophy. No gender differences were observed in the global prevalence of BPC (p = 0.649). However, significantly more women reported lipoatrophy of the lower limbs (p = 0.009) and buttocks (p = 0.007), as well as lipohypertrophy (p = 0.007), than men; 58.2% (95% CI: 54.0-62.4) patients noted that BPC negatively affected their daily activities. This study reflects the high prevalence of patient and physician-perceived BPC in the HIV population, and the adverse impact on daily life. Physicians should be aware of the psychosocial consequences of BPC in HIV patients in order to improve patient well-being.

Safety and antiviral response at 12 months of lopinavir/ritonavir therapy in human immunodeficiency virus-1-infected children experienced with three classes of antiretrovirals

INTRODUCTION

Many human immunodeficiency virus type 1 (HIV-1)-infected children have already failed treatment with 2 or even 3 classes of antiretrovirals. Coformulation of lopinavir with low dose ritonavir exhibits a potent antiretroviral effect. However, the data in heavily pretreated children are still scarce. This study evaluated the safety and effectiveness of combination therapy including lopinavir/ritonavir in children with prior exposure to all classes of oral antiretrovirals.

METHODS

This was an open label multicenter observational study, in which data were reviewed according to a standardized protocol. The study population included all HIV-1-infected children with virologic failure (HIV-1 RNA >5000 copies/mL) followed in 12 Spanish hospitals for >12 months, experienced with the 3 classes of oral antiretrovirals, in whom a lopinavir/ritonavir-containing regimen was started.

RESULTS

By March 2003, 45 patients had been treated with lopinavir/ritonavir for a median of 18 months (range, 3-28). The median age at baseline was 9.7 years (range, 4.3-17.1). The median times of prior treatment were 88 months (range, 31-145) with nucleoside reverse transcription inhibitors and 42 months (range, 19-63) with protease inhibitors. Twenty-five patients were classified as Centers for Disease Control and Prevention clinical category C. Median values for absolute and percentage CD4 at baseline were 501 (range, 6-1512) and 19% (range, 0.5-49), respectively, and plasma HIV-RNA was 5.0 log10 copies/mL (range, 4.1-6.1). During follow-up, 11 (24%) children switched from liquid to solid formulation. At 48 weeks, the median values for absolute and percentage CD4 increased by 199 cells/microL and 3%, respectively, and median plasma viral load declined 1.75 log10 copies/mL. Forty-two percent of children achieved a plasma RNA of <400 copies/mL (intent to treat analysis). Baseline genotypic resistance was available in 40 children. Nonresponders had 7.0 +/- 1.6 protease inhibitor-associated mutations at baseline compared with 4.8 +/- 1.7 in children achieving virologic suppression (P = 0.06). Adverse events were described in 18 children. Three children permanently discontinued and 4 transiently withdrew lopinavir/ritonavir. At 12 months, there were mild but not significant increases in plasma cholesterol and triglycerides.

CONCLUSIONS

Lopinavir/ritonavir when given as part of salvage regimen is well-tolerated, although switching to pills is frequently required. The regimen has a potent and durable antiretroviral activity in most heavily pretreated children, despite the presence of multiple mutations to all classes of oral antiretrovirals.

Immunological changes after highly active antiretroviral therapy with lopinavir-ritonavir in heavily pretreated HIV-infected children

We evaluated the effect of salvage antiretroviral therapy with lopinavir/ritonavir (LPV/r) on the immune system of heavily antiretroviral pretreated HIV-infected children. We carried out a longitudinal study in 20 antiretroviral experienced HIV-infected children to determine the changes in several immunological parameters (T cell subsets, thymic function) every 3 months during 18 months of follow-up on salvage therapy with LPV/r. Statistical analyses were performed with the Wilcoxon test, taking as a reference the basal value at the entry in the study. HIV-infected children showed an increase of CD4+ T cells, a decrease in CD8+ T cells, and an increase in T cell rearrangement excision circle (TRECs) levels. The percentage of HIV children with undetectable viral load (VL < or = 400 copies/ml) increased significantly (p = 0.007) and the percentage with SI viral phenotype decreased significantly (p = 0.002) at the end of the study. Thus, the viral phenotype changed to NSI/R5 after salvage therapy with LPV/r. Interestingly, we observed a significant decrease of memory (CD4+ CD45RO+) and a moderate decrease of activated (CD4+ HLA-DR+, CD4+ HLA-DR+CD38, CD4+, CD45RO+HLA-DR+) CD4+ T cells during the follow-up. On the other hand, memory (CD8+ CD45RO+ and CD8+ CD45RO+CD38+), activated (CD8+ HLA-DR+CD38+, CD8+ HLA-DR+, CD8+ CD38+), and effector (CD8+ CD57+, CD8+ CD28(-)CD57+) CD8+ T cells had a very significant decrease during follow-up. Our data indicate an immune system reconstitution in heavily pretreated HIV-infected children in response to salvage therapy with LPV/r as a consequence of a decrease in immune system activation and an increase in thymic function.

Positive virological outcome after lopinavir/ritonavir salvage therapy in protease inhibitor-experienced HIV-1-infected children: a prospective cohort study

BACKGROUND

Lopinavir/ritonavir has demonstrated antiviral activity in the HIV-infected patient.

OBJECTIVE

To analyse virological response to lopinavir/ritonavir therapy in previously protease inhibitor (PI)-experienced HIV-1-infected children.

MATERIALS AND METHODS

Sixty-seven HIV-1-children on lopinavir/ritonavir were studied in a multicentre prospective cohort observational study. The outcome variables were undetectable viral load (uVL; VL < or =400 copies/mL) and virological failure after uVL with a rebound of VL >400 copies/mL. VL and genotype of HIV-1-isolates were measured using standard assays.

RESULTS

83.5% of children had a 1 log10 VL decrease including 65.6% who reached uVL. Children with >2 changes of antiretroviral therapy (ART) or >5 drugs needed a median time of 3-4 months higher than children with < or =2 changes of ART or < or =5 drugs previous to lopinavir/ritonavir, to reach those values, and the relative proportions (RP) were 2.2 (P =0.038) and 1.9 (P=0.050), respectively. Children with CD4+>15% (P=0.122), VL < or =30,000 (P < 0.001) copies/mL, and age >12 years (P=0.096) achieved an earlier control of VL during the follow-up. The children with virological failure or rebound of VL had higher baseline VL and lower CD4+ T-lymphocytes/mm3 and had taken a greater number of drugs previous to lopinavir/ritonavir. HIV-children with a new nucleoside reverse transcriptase inhibitor (NRTI), or protease inhibitor (PI) or PI plus non-nucleoside reverse transcriptase inhibitors (NNRTI) in the current regimen had a better virological response than children without these new drugs. Also, children with <6 protease mutations had an RP of 2.31 of achieving uVL.

CONCLUSIONS

Highly active antiretroviral therapy (HAART) including lopinavir/ritonavir induces beneficial effects in terms of virological outcome responses, and it is an effective option for salvage therapy in PI-experienced HIV-1-infected children.

Salvage lopinavir-ritonavir therapy in human immunodeficiency virus-infected children

OBJECTIVE

To study the control of viral replication in human immunodeficiency virus (HIV)-infected children on different salvage therapies.

DESIGN AND SETTING

A retrospective observational study in 120 HIV-infected children was conducted. The children were divided into 3 groups according to their salvage therapies: (1) children receiving first line highly active antiretroviral therapy (HAART); (2) protease inhibitor-experienced children receiving second line HAART; (3) protease inhibitor-experienced children receiving HAART including lopinavir-ritonavir (LPV/r). The outcome variables examined were time to achieve viral load (VL) < or =400 copies/mL, success in achieving VL < or =400 copies/mL and time to virologic failure (VL >400 copies/mL).

METHODS

VL (HIV-RNA copies/mL) was quantified with reverse transcription-polymerase chain reaction molecular assay. For each protocol, survival analyses were conducted to determine the probability of achieving VL < or =400 copies/mL and rebound of VL.

RESULTS

VL < or =400 copies/mL was achieved by 52.4% of children receiving first line HAART, 48.3% receiving second line HAART and 71.5% receiving HAART including LPV/r. Children receiving HAART including LPV/r reached VL < or =400 copies/mL in a shorter time than children receiving second line HAART (P = 0.017), but quite similar to children receiving first line HAART. In terms of adjusted relative risk, children receiving HAART including LPV/r were 3.36 [95% confidence interval (95% CI), 1.59, 7.07] more likely to achieve VL < or =400 copies/mL than children receiving a different second line HAART. VL rebound occurred in 68.2% children receiving first line HAART, 73.4% receiving second line HAART and 32.4% receiving HAART including LPV/r. Children receiving HAART that includes LPV/r has less incidence of VL rebound (P=0.013) and 3.29 (95% CI 1.04, 10.3) times less risk to achieve a VL rebound than children receiving a different second line HAART.

CONCLUSIONS

HAART that includes LPV/r is able to control HIV replication more efficiently than other classic salvage antiretroviral therapies.

Virological phenotype switches under salvage therapy with lopinavir-ritonavir in heavily pretreated HIV-1 vertically infected children

OBJECTIVE

To investigate the effects of salvage therapy with lopinavir-ritonavir on HIV-1 phenotype in heavily antiretroviral experienced HIV-infected children.

DESIGN

Twenty antiretroviral experienced HIV-infected children were studied during a mean of time of 16.1 months from initiation of the treatment with lopinavir-ritonavir.

METHODS

Besides CD4 T cells, viral load and clinical status, we analyzed 91 serial viral isolates to study the phenotype, and biological clones derived from co-cultivation techniques.

RESULTS

We observed an increase in CD4 T cells, a statistically significant decrease in viral load and clinical benefits from 3 months after treatment. Ninety per cent of children had SI/X4 bulk isolates in peripheral blood mononuclear cells at study entry. The viral phenotype changed to non syncitium-inducing (NSI)/R5 in 94% of the children after a mean of 5.7 months (95% confidence interval, 2.1-9.3 months) of salvage therapy. The remaining 10% of children had NSI/R5 isolates at entry and at all follow-up study. Similar results were found at the clonal level. Thus, at study entry in PBMC of three children with bulk syncitium-inducing (SI) phenotype, we recovered 65 biologic clones, 56 being SI and nine NSI. After salvage therapy bulk isolates changed to NSI and of 40 biologic clones recovered only five were SI and the rest were NSI.

CONCLUSIONS

Our data suggest that lopinavir-ritonavir salvage therapy led not only to a viral load decrease but also to a phenotypic change. X4 virus appeared to be preferentially suppressed. Shifts in co-receptor usage may thereby contribute to the clinical efficacy of anti-HIV drugs in vertically infected infants.

Detection methods of the drug-addiction and alcoholism treatment programme of the Spanish National Railway Company (RENFE)

BACKGROUND

Social problems in enterprises need to be approached by all groups involved in order to achieve a satisfactory result. With regard to Occupational Health and, specifically, drug-addiction, the groups concerned are Occupational Health Services, Trade Unionists and Managers.

OBJECTIVES

To analyse the involvement of the social groups (Occupational Health Service, Management and Trade Unions) in relation to the detection of workers suffering from drug-addiction and/or alcoholism.

METHODS

During the first eight years of implementation (1990-1997) of the Drug-Addiction and Alcoholism Treatment Programme of the Spanish National Railway Company (RENFE), a total of 477 workers consuming alcohol and drugs were detected and treated under the Programme (1.1% prevalence), 465 men (97.5%) and 12 women (2.5%), with an average age of 39.8 years.

RESULTS

The subjects were detected by occupational physicians (55.4%), occupational psychologists (2.9%), managers (11.3%), trade unionists (19.5%), via self-referral (9.4%) and by other means (1.5%).

CONCLUSIONS

The results demonstrate the efficiency and the profitability to the company of prevention and treatment interventions and the need for the coordination of managers, trade unions and occupational health services.

Differential capacity of various anti-Ig reagents to synergize with interleukin-4 to induce clonal expansion in resting and activated B cells

The regulation of B cell growth responses by cross-linking of surface Ig receptors by monoclonal or polyclonal antibodies and its interaction with interleukin-4 (IL-4) has been evaluated. High-density B cells from autoimmune NZB/W mice were proliferated in the presence of low concentrations of a polyclonal goat anti-mu antibody and IL-4. Similarly, slight but significant positive responses were obtained with anti-K monoclonal antibodies and IL-4. In contrast, the same concentration of other surface Ig binding agents such as monoclonal antibodies against mu and delta immunoglobulin heavy chains did not synergize with IL-4 in order to induce clonal expansion of resting B cells. Polyclonal and monoclonal anti-Ig reagents inhibited the spontaneous cell growth of low-density B cells (in vivo activated B cells), although the negative effect was less noticeable with anti-delta monoclonal antibodies. Upon addition of IL-4 to activated B cell cultures in the presence of goat anti-mu antibody, a significant proliferative response was obtained. However, this lymphokine was unable to induce clonal expansion of B cell blasts in the presence of the various monoclonal anti-Ig antibodies employed in this study. Similar results were obtained with splenic B cells from normal animals, suggesting that the results shown in this report are not due to putative functional peculiarities of autoimmune B cells.

The requirements for growth of in vivo activated autoimmune B cells are similar to those of in vitro generated lipopolysaccharide B cell blasts and dissimilar to anti-IgM plus IL-4 induced B lymphoblasts

The requirements for growth of in vivo activated B cells (natural blasts) from autoimmune NZB/W mice and of B cells from the same animals activated in vitro with either LPS or anti-IgM plus IL4 (mimicking 'in vitro' antigen induced TH cell-B cell interaction) were studied comparatively. The proliferation of natural and LPS blasts was inhibited by anti-IgM antibodies and augmented by recombinant IL-5. In contrast, anti-IgM stimulated the growth of anti-IgM plus IL-4 primed B cells but was without effect on the proliferative responses in the presence of IL-5. The growth inhibition induced by anti-IgM signalling on natural and LPS blasts seemed to be due to cross-linking of sIg rather than to binding of anti-IgM antibodies to the Fc receptors since a similar effect was observed with the F(ab)'2 fragment of this molecule. Maximum proliferation was obtained by a combination of IL-4 and IL-5 in natural and LPS blasts, whereas peak responses in anti-IgM plus IL-4 blasts were achieved by a combination of anti-IgM and IL-4. Lymphoblasts recovered after preculturing natural blasts in medium alone (more differentiated in vivo activated B cells) displayed high spontaneous proliferation which was strongly inhibited by anti-IgM. This inhibition was reversed partially by IL-4 and totally by IL-5. To define better the role of BLy+ cells in the spleen of NZB/W mice, purified Ly1+ and Ly1- cells, obtained by separation using magnetic beads, were analysed. The growth of both cell subpopulations was inhibited by anti-IgM and enhanced by IL-5. Cytotoxic elimination of Ly1+ cells from the primed B blast populations did not modify the proliferative pattern of these cells. Our results show that the growth requirements of in vivo activated autoimmune B cells resemble those of LPS blasts and differ from those following stimulation with anti-IgM plus IL-4, suggesting that B cells in systemic autoimmune diseases may have been activated by polyclonal stimulation. Nevertheless, other mechanisms for autoimmune B cell activation cannot be ruled out by the present experimental approach.

Protein kinase C-independent expression of stromelysin by platelet-derived growth factor, ras oncogene, and phosphatidylcholine-hydrolyzing phospholipase C

Changes in the expression of several genes play critical roles in cell growth and tumor transformation. A number of proteases are increased in some tumors, and the level of these enzymes correlates with the metastatic potential of several cancer cell lines. Stromelysin, with the widest substrate specificity, can degrade the extracellular matrix conferring metastatic potential to tumor cells. The mechanisms whereby growth factors and oncogenes control the expression of stromelysin are beginning to be characterized. In the study shown here we also identify a region in the stromelysin promoter which is involved in the induction of stromelysin in response to platelet-derived growth factor, phosphatidylcholine-hydrolyzing phospholipase C, and ras oncogene. Our results are consistent with the notion that platelet-derived growth factor/phosphatidylcholine-hydrolyzing phospholipase C induces stromelysin gene expression through a phorbol myristate acetate/protein kinase C-independent mechanism by acting through elements in the stromelysin promoter distinct from the 12-O-tetradecanoylphorbol-13-acetate-responsive element.

Interleukin 2 production in a family with systemic lupus erythematosus and a C4Q0 heterozygous inheritance

Interleukin 2 production was studied in a family with systemic lupus erythematosus (SLE) and a C4Q0 heterozygous inheritance. Autoimmune manifestations seemed to be associated with the HLA haplotype containing the C4Q0 allele, which was shared by all four ill family members. Concentrations of interleukin 2, however, did not associate either with the haplotype or with the clinical or serological manifestations, as diminished concentrations of interleukin 2 were found in only two subjects with SLE. Thus the defect in this family seemed to be acquired rather than genetically conditioned.

Lack of correlation between in vitro immunological alterations and the development of scleroderma-like skin lesions in toxic oil syndrome patients

We examined whether immunological disturbances could influence the development of scleroderma-like skin lesions in patients affected by the Spanish toxic oil syndrome (TOS). To this end, peripheral blood mononuclear cells (PBMC) were collected from 13 chronic patients and 8 control subjects. All patients had suffered a toxic-induced severe neuromyopathy, and 6, in addition, had developed sclerodermoid skin manifestations. The phenotypic profile and the concentrations of interleukin-2 (IL-2) and of molecules with B cell differentiation factor IgG activity (BCDF-IgG) in supernatants of phytohemagglutinin-stimulated lymphocytes were analyzed both in patients and in normal controls. Molecules with BCDF-IgG activity were found increased in supernatants of mitogen-stimulated lymphocytes from TOS patients. Concentrations of IgG secreted by staphylococcus aureus-SAC-B blasts in the presence of TOS PBMC supernatant was 88 +/- 32.62 ng/ml (mean +/- 1 SD) versus 53 +/- 5.34 ng/ml in the presence of control supernatant (p less than 0.01). Levels of BCDF-IgG activity in TOS PBMC supernatants positively correlated with IgG serum levels (r = 0.69, p less than 0.01). The phenotypic profile of lymphocyte populations and the production of IL-2 were not altered in TOS subjects. No statistically significant differences were observed in the lymphocyte distribution nor in the IL-2 and BCDF-IgG production when comparing patients with or without scleroderma-like skin lesions. The results indicate that there was a dysfunction of the immune response in TOS subjects, which, however, was not sufficient for the development of the sclerodermoid lesions.

A role for T3+4-6-8- transitional thymocytes in the differentiation of mature and functional T cells from human prothymocytes

In vivo, immunocompetent T lymphocytes are only detected late in ontogeny, among mature thymocytes expressing either T4 (L3T4 in mouse) or T8 (Lyt-2) surface glycoproteins. We have previously shown, however, that there are functional precursors among T3+4-6-8- human thymocytes in vivo. Here we report on the in vitro differentiation of prothymocytes into T3+4-6-8- and mature T cells. T11+3-4-6-8- prothymocytes (0.5% of total thymocytes, greater than 98% pure) were obtained after treatment of thymocytes with OKT3 (T3), OKT4A (T4), Na1/34 (T6), and B9.4 (T8) monoclonal antibodies plus complement. During culture, the prothymocyte precursors acquire first T3 and then either T4 or T8, but not T6. The largest subpopulation in the thymus, T4+6+8+ cells, are not detected among the in vitro T-cell precursors. During culture, the precursors acquire cytolytic activity as soon as they express either the T3+4-6-8- or the mature (T3+4+8- or T3+4-8+) phenotypes. We suggest that T3+4-6-8- cells are a productive, transitional stage in T-lymphocyte development.

Differentiation of human mature thymocytes: existence of a T3+4-8- intermediate stage

A T3 complex-bearing subpopulation was characterized within an in vivo cycling T4-8- early thymocyte compartment which contains cells constitutively expressing interleukin 2 and transferrin receptors. We show differentiation in vitro of both mature subsets of thymocytes (T3+4+8- and T3+4-8+) from the above T4-8- compartment, their appearance being preceded by cells in a T3+4-8- intermediate stage. Furthermore, those mature thymocytes generated in vitro contain functionally competent cells which use T3, T4 and T8 structures for their cytolytic activity. The finding of T3+4-8- thymocytes in vivo, together with the observation that T3 antigen expression precedes that of T4 or T8 molecules in vitro, shows that T3 (and presumably Ti) is present early in ontogeny, and suggests that T3+4-8- cells constitute an "intermediate" stage relevant to the connection between early precursors and mature thymocytes during T lymphocyte ontogeny.