Frequency Of Memory CD4 Research Articles

T cell response to influenza vaccination remains intact in adults with congenital heart disease who underwent early thymectomy

IntroductionT cells developed in the thymus play a key role in vaccine immunity. Thymectomy occurs during infant congenital heart surgery and results in an altered T cell distribution. We investigated if adults with congenital heart disease (ACHD) who underwent early thymectomy have a diminished response to influenza vaccination. MethodsBlood samples from ACHD with early thymectomy ≤1 year of age (ACHD-ET; n = 12), no thymectomy (ACHD-NT; n = 8), and healthy controls (HC; n = 14) were collected prior to and 4 weeks after influenza vaccination. Flow cytometric analysis of T cell subsets and vaccine-specific cytokine expressing CD4+ T cells as well as hemagglutination inhibition (HI) assays were completed. ResultsThe mean age of the cohort was 34 ± 10.6 years and similar in all groups. The mean frequencies of naïve CD4+ and CD8+ T cells were lower in ACHD-ET than in HC (32.7% vs. 46.5%, p = 0.027 and 37.2% vs. 57.4%, p = 0.032, respectively). There was a rise in the frequency of memory CD4+ and CD8+ T cells in the ACHD-ET group. The ACHD-NT had no statistical difference from either group. The frequencies of influenza-specific memory CD4+ T cells expressing IFN-γ and TNF-α were increased after vaccination across all groups (p < 0.05). ConclusionsACHD-ET have fewer naïve T cells, suggesting immunosenescence. Despite this, they show an adequate T Cell response to vaccination in young adulthood. Our findings support that routine vaccination is effective in this population, but research into older ACHD is necessary.

Role of Circulating T Follicular Helper Cells and Stem-Like Memory CD4+ T Cells in the Pathogenesis of HIV-2 Infection and Disease Progression.

CD4+ T cells are critical players in the host adaptive immune response. Emerging evidence suggests that certain CD4+ T cell subsets contribute significantly to the production of neutralizing antibodies and help in the control of virus replication. Circulating T follicular helper cells (Tfh) constitute a key T cell subset that triggers the adaptive immune response and stimulates the production of neutralizing antibodies (NAbs). T cells having stem cell-like property, called stem-like memory T cells (Tscm), constitute another important subset of T cells that play a critical role in slowing the rate of disease progression through the differentiation and expansion of different types of memory cell subsets. However, the role of these immune cell subsets in T cell homeostasis, CD4+ T cell proliferation, and progression of disease, particularly in HIV-2 infection, has not yet been elucidated. The present study involved a detailed evaluation of the different CD4+ T cell subsets in HIV-2 infected persons with a view to understanding the role of these immune cell subsets in the better control of virus replication and delayed disease progression that is characteristic of HIV-2 infection. We observed elevated levels of CD4+ Tfh and CD4+ Tscm cells along with memory and effector T cell abundance in HIV-2 infected individuals. We also found increased frequencies of CXCR5+ CD8+ T cells and CD8+ Tscm cells, as well as memory B cells that are responsible for NAb development in HIV-2 infected persons. Interestingly, we found that the frequency of memory CD4+ T cells as well as memory B cells correlated significantly with neutralizing antibody titers in HIV-2 infected persons. These observations point to a more robust CD4+ T cell response that supports B cell differentiation, antibody production, and CD8+ T cell development in HIV-2 infected persons and contributes to better control of the virus and slower rate of disease progression in these individuals.

Gut Dysbiosis Thwarts the Efficacy of Vaccine Against Mycobacterium tuberculosis.

The generation of enduring protective immunity by vaccines is of utmost importance. Intriguingly, there is considerable variation in the efficacy of vaccines amongst individuals. Various studies have shown that normal flora of gastrointestinal tract plays a vital role in maintaining host homeostasis and immunity. Since gut microbiome is also extremely variable between individuals, we speculate that it might impact individual’s response to vaccines. Consequently, we administered broad spectrum antibiotics cocktail to induce gut dysbiosis and monitored its impact on the generation of long-lasting memory T cells and thereby BCG vaccine efficacy. Interestingly, gut dysbiosis significantly decreased the activation of CD4+ T cells and CD8+ T cells. Further, there was decline in the frequency of memory CD4+ T cells and CD8+ T cells in lungs and secondary lymphoid organs of the vaccinated animals. Moreover, it dampened the IFN-γ and TNF-α secretion and proliferation of Mtb-specific T cells. Most importantly, dysbiosis hampered Mtb clearance in vaccinated animals, as evidenced by increase in the colony forming units (CFUs) in lungs and spleen. Our findings indicate that gut dysbiosis can be one of the major factors responsible for variable efficacy of TB vaccines across the world.

Gut microbiota and clinical outcomes treated with nivolumab in Chinese non-small cell lung cancer.

2614 Background: Gut microbiome affecting responses to immune checkpoint inhibitors (ICIs) against non-small cell lung cancer (NSCLC) has been investigated in western population. However, considering genetic variation, this phenomenon remains in vague in east-Asian NSCLC population. The study is designed to explore the relationships between gut microbiome and clinical outcomes treated with anti-PD-1 blockade in Chinese patients. Methods: 37 NSCLC patients received the treatment of Nivolumab were enrolled in the study from the clinical trials CheckMate870 (NCT03195491). Fecal samples were collected at the starting point, every time point performing clinical evaluation and that with disease progression. 16s sequencing was applied to assess the gut microbiota characteristics. Peripheral immune profiles were determined by multi-color flow cytometry in parallel. Results: When subgrouping patients into responders (R) and non-responders (NR) groups according to the clinical response assessed by RECIST1.1, patients in R group harbored higher diversity of gut microbiome at the starting point with consistent composition along the treatment. Analyzing progression-free survival (PFS) according to RECIST 1.1, patients with higher microbiome diversity had significantly prolonged PFS when compared to those with low diversity. Compositional difference was observed between two groups as well with the enrichment of Alistipes putredinis, Bifidobacterium logum, Prevotella corpri in R group whereas Ruminococcus_unclassified in NR group. Analysis of systemic immune responses using multi-color flow cytometry revealed that patients with a high abundance of microbiome diversity in the gut had more frequencies of memory CD8+ T cell subset in the periphery in response to anti-PD-1 therapy. Conclusions: Our results report the strong correlation between the gut microbiome diversity and the responses to anti–PD-1 immunotherapy in Chinese NSCLC patients regardless of genetic variation between Western and Chinese population. Patients with a favorable gut microbiome (such as high diversity) have enhanced immune responses mediated by effector T cell function in the periphery. These findings thus provide important implications for the prediction and the evaluation of anti-PD-1 immunotherapy against NSCLC.

Changes in T cell immunity in patients with metastatic castration resistant prostate treated with Radium-223 treatment.

295 Background: The bone seeking calcium mimetic, Radium223 (Ra223), emits high energy alpha particle that cause irreparable double strand DNA breaks in osseous metastases. Ra223 improves survival in patients with bone-predominant metastatic castration resistant prostate cancer (mCRPC). The effect of Ra223 on the host immune system, and T cell immunity in particular, is unknown. Methods: Eligible patients include men with mCRPC, osseous metastases and a clinical indication for Ra223 were eligible. Blood samples were collected at the following time points: prior to the first, second, and fourth treatments (tx) and 4 weeks after the sixth dose. Peripheral blood mononuclear cells (PBMCs) were purified and stained with a cocktail of antibodies to surface and effector immune molecules. Some PBMCs were stimulated and stained for intracellular cytokines (IFN-g, TNF-a, IL-13, IL-17, and IL-21). Stained cells were analyzed by flow cytometry. Results: A total seven patients completed at least two sample collections. The median number of prior lines of therapy was three. Median age was 71 (55-79). Median PSA was 78 (2-351). Effector memory (EM) CD8+ T cells were divided into two subsets expressing high and low levels of the IL-7 receptor alpha chain (IL-7Ra) with distinct cellular characteristics including perforin expression. The frequency of IL-7Rahigh and low EM CD8+ T cells expressing programmed death protein 1 (PD-1) was decreased after Ra223 treatment (pre vs. post, median (%) ± interquartile range, 14.3 ± 12.9 vs. 7.2 ± 20.9, P = 0.03; 16.7 ± 28.8 vs. 14.1 ± 37.8, P = 0.015 by Wilcoxon matched-pairs signed rank test). A similar finding was observed in the frequency of memory CD4+ T cells expressing PD-1 after the treatment (median (%) ± interquartile range, 7.2 ± 7.7 vs. 3.9 ± 3.4, P= 0.03). Conclusions: In this preliminary cohort of patients, Ra223 tx was associated with decrease in PD-1 expression by effector T cells. Further investigations of an immune mechanism of Ra223 mediated antitumor activity are warranted.

Bortezomib Inhibits Osteoclastogenesis and Bone Resorption Through Modulation of CHIT1 and YKL40 Expression

Background: VSIG4 acts as a co-inhibitory ligand to negatively regulate T cell proliferation and cytokine production by arresting cell cycle at G0/G1 phase and upregulating tolerance-inducing p27KIP-1. VSIG4 expression is restricted to macrophages. VSIG4 fusion protein also inhibits T cell production of Th1, Th2, and Th17 cytokines. Thus, we hypothesized that endogenous VSIG4 impairs helper T cell functions and then inhibits the subsequent antibody response. Materials and Methods: Mice were immunized subcutaneously with 100 g ovalumin (OVA) in a 1:1 emulsion with phosphate-buffered saline (PBS) and CFA in 100 l PBS. OVAspecific IgM or IgG subclasses were determined using culture supernatants or sera from immunized mice with OVA-coated plates and horseradish peroxidase-conjugated anti-mouse IgG1, -IgG2a, -IgG2b, and -IgG3. To study the VSIG4 role in antibody class switching via regulation of helper T cells, BALB/c mice were immunized intraperitoneally with 500 g of 2,4,6-Trinitrophenyl hapten (TNP)Keyhole Limpet Hemocyanin (KLH) for 14 days. Isolated B cells from TNP-KLH-immunized mice and purified CD4+ T cells from BALB/c wild-type or VSIG4 KO mice immunized s.c. with OVA/CFA were cocultured in the presence of TNPOVA (50 ng/ml) for 5 days. Culture supernatants were collected, and ELISA was performed on a TNP-CGG (100 g/ml)-coated plate to measure anti-TNP IgM and IgG titers. Results: Isotype switching of OVA-specific antibody subclasses to IgG1, IgG2a, IgG2b, and IgG3 was enhanced in OVA-immunized VSIG4 KO mice. 2,4,6-TNPe KLH-primed B cells cocultured with OVAprimed CD4+ T cells from OVA-immunized VSIG4 KO mice in the presence of TNP-OVA showed enhanced isotype switching to IgG subclasses compared to those cocultured with cells isolated from OVA-immunized wild-type (WT) mice. Furthermore, the levels of CD40L expression, the frequency of memory CD4+ T cells, and the production of isotype switching-inducing cytokines increased significantly in OVA-primed CD4+ T cells from VSIG4 knockout (KO) mice. T cells from OVA-specific T cell receptor transgenic mice produced more IFNwhen cocultured with macrophages from VSIG4 KO mice compared to WT mice. Conclusion: Our results demonstrate that macrophage-associated VSIG4 plays a negative role in helper T cell-dependent isotype switching by inhibiting helper T cell activation and differentiation, and suppressing the isotype switching-inducing cytokine production in antigen-primed CD4+ helper T cells.

PWE-123 Adaptive immune responses in ALF

<h3>Introduction</h3> Acute liver failure (ALF) is characterised by an overwhelming hepatic necrosis, imuneparesis and susceptibility to infections. To date, a number of defects in innate immune responses have been identified but defects in adaptive immune responses remain unexplored. The aims of this study were to evaluate whether impairment in adaptive immune responses could also account for the immuneparesis and infection susceptibility in ALF. <h3>Method</h3> CD4⁺T-cell-subsets in peripheral blood mononuclear cells (PBMCs) from 20 ALF patients and 10 healthy controls (HC) were determined using multicolor flow cytometry. CD45RA/RO were used to differentiate naïve and memory CD4⁺T-cells. Expression or lack of expression of CD45RO/CCR7 was used to determine effector memory (T_EM) subset. Negative regulators of T cell activation (CTLA-4) were analysed. Specific CD4⁺T-cell antigen-recall responses to a pool of HLA class II-restricted T cell epitopes were examined <i>in vitro </i>in the presence or absence of anti-CTLA-4 blocking antibody. CD4⁺T-cell proliferation was assessed by flow cytometry and IL-2 secretion by ELISA. Soluble CTLA-4 (sCTLA-4) in sera samples were measured using ELISA. <h3>Results</h3> Whilst overall percentages of circulating CD4+ T lymphocytes were expanded in ALF (p=0.03), we report a significant reduction in the frequency of memory CD4⁺T-cell population (p=0.01). MELD score correlated negatively with the proportion of CD4⁺T-cells (r=-0.462, p=0.06). Furthermore, T_EMpopulation was significantly reduced in ALF in comparison to HC (p=0.04). This reduction was highly significant in patients with a poor outcome (p=0.002). CTLA-4 expressing CD4⁺T-cells were significantly higher in ALF compared to HC (p=0.0001). Similarly, levels of sCTLA-4 in the sera of ALF were significantly elevated (p= 0.02). ALF (n = 4) showed a defect in proliferative responses to recall antigens compared to HC (n = 3) (p = 0.05). However, blockade of CTLA-4-4 was sufficient to restore antigen-recall responses defined by increased T cell proliferation (p=0.05) and IL-2 secretion (0 vs 20.84 pg/ml). <h3>Conclusion</h3> Our novel data identify defects in function of circulating CD4⁺T-cell subsets in ALF with a significant increase in the CTLA-4 expressing CD4⁺T-cells, a phenotype with an inhibitory functional aspect. Proof-of-principle experiments indicate that blocking CTLA-4, a crucial immune checkpoint, may be a promising immunotherapeutic target to boost adaptive immune responses and reduce susceptibility to infection in ALF patients. <h3>Disclosure of interest</h3> None Declared.

Endogenous VSIG4 negatively regulates the helper T cell-mediated antibody response

VSIG4 acts as a co-inhibitory ligand to negatively regulate T cell proliferation and cytokine production, and its expression is restricted to macrophages. We hypothesized that endogenous VSIG4 impairs helper T cell functions and then inhibits the subsequent antibody response. Isotype switching of ovalbumin (OVA)-specific antibody subclasses to IgG1, IgG2a, IgG2b, and IgG3 was enhanced in OVA-immunized VSIG4 knockout (KO) mice. 2,4,6-Trinitrophenyl hapten (TNP) – Keyhole Limpet Hemocyanin (KLH)-primed B cells cocultured with OVA-primed CD4+ T cells from OVA-immunized VSIG4 KO mice in the presence of TNP-OVA showed enhanced isotype switching to IgG subclasses compared to those cocultured with cells isolated from OVA-immunized wild-type (WT) mice. Furthermore, the levels of CD40L expression, the frequency of memory CD4+ T cells, and the production of isotype switching-inducing cytokines increased significantly in OVA-primed CD4+ T cells from VSIG4 KO mice. T cells from OVA-specific T cell receptor (TCR) transgenic mice produced more IFN-γ when cocultured with macrophages from VSIG4 KO mice compared to WT mice. Thus, our results demonstrate that macrophage-associated VSIG4 plays a negative role in helper T cell-dependent isotype switching by inhibiting helper T cell activation and differentiation, and suppressing the isotype switching-inducing cytokine production in antigen-primed CD4+ helper T cells.

Friends not foes: CTLA-4 blockade and mTOR inhibition cooperate during CD8+ T cell priming to promote memory formation and metabolic readiness.

During primary Ag encounter, T cells receive numerous positive and negative signals that control their proliferation, function, and differentiation, but how these signals are integrated to modulate T cell memory has not been fully characterized. In these studies, we demonstrate that combining seemingly opposite signals, CTLA-4 blockade and rapamycin-mediated mammalian target of rapamycin inhibition, during in vivo T cell priming leads to both an increase in the frequency of memory CD8(+) T cells and improved memory responses to tumors and bacterial challenges. This enhanced efficacy corresponds to increased early expansion and memory precursor differentiation of CD8(+) T cells and increased mitochondrial biogenesis and spare respiratory capacity in memory CD8(+) T cells in mice treated with anti-CTLA-4 and rapamycin during immunization. Collectively, these results reveal that mammalian target of rapamycin inhibition cooperates with rather than antagonizes blockade of CTLA-4, promoting unrestrained effector function and proliferation, and an optimal metabolic program for CD8(+) T cell memory.

The Frequency of α4β7 high Memory CD4+ T Cells Correlates With Susceptibility to Rectal Simian Immunodeficiency Virus Infection

Integrin α₄β₇(high) (α₄β₇(high)) mediates the homing of CD4⁺ T cells to gut-associated lymphoid tissues, which constitute a highly favorable environment for HIV expansion and dissemination. HIV and simian immunodeficiency virus (SIV) envelope proteins bind to and signal through α₄β₇(high) and during acute infection SIV preferentially infects α₄β₇(high) CD4⁺ T cells. We postulated that the availability of these cells at the time of challenge could influence mucosal SIV transmission and acute viral load (VL). We challenged 17 rhesus macaques with 3000 TCID50 of SIVmac239 rectally and followed the subsets of α₄β₇(high) T cells and dendritic cells (DCs) by flow cytometry in blood and tissues, before and after challenge. We found that the frequency of memory CD4⁺ T cells that expressed high levels of α₄β₇(high) (α₄β₇(high) memory CD4⁺ T cells) in blood before challenge correlated strongly with susceptibility to infection and acute VL. Notably, not only at the time of challenge but also their frequency 3 weeks before challenge correlated with infection. This association extended to the rectal tissue as we observed a strong direct correlation between the frequency of α₄β₇(high) memory CD4⁺ T cells in blood and rectum before and after challenge. The frequency of α4β7 myeloid DCs and α₄β₇(high) CD80⁺ DCs also correlated with infection and acute VL, whereas blood CCR5⁺ and CD69⁺ CD4⁺ T cells could not be associated with infection. Our results suggest that animals with higher frequency of α₄β₇(high) CD4⁺ T cells in circulation and in rectal tissue could be more susceptible to SIV rectal transmission.

Immunologic response and memory T cells in subjects cured of tegumentary leishmaniasis

BackgroundThe main clinical forms of tegumentary leishmaniasis are cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML). L.braziliensis infection is characterized by an exaggerated production of IFN-gamma and TNF-alpha, cytokines involved in parasite destruction, but also in the pathology. Maintenance of an antigen-specific immune response may be important for resistance to re-infection and will contribute for vaccine development. In the present work we investigated the immune response in CL and ML cured individuals.MethodsParticipants in the present study included 20 CL and 20 ML patients, who were evaluated prior to, as well as 2 to 15 years after therapy. IFN-gamma, IL-2 and TNF-alpha production were determined by ELISA in supernatants of mononuclear cells stimulated with soluble L.braziliensis antigen (SLA). The frequency of memory CD4+ T cell populations was determined by FACS.ResultsHere we show that the majority of CL and ML patients did not produce in vitro IFN-gamma in response to SLA after cure. In the cured individuals who responded to SLA, effector memory (CD45RA-CCR7-) CD4+ T cells were the ones producing IFN-gamma. Because a large percent of CL and ML cured patients lost SLA-induced IFN-gamma production in peripheral blood, we performed Leishmania skin test (LST). A positive LST was found in 87.5% and 100% of CL and ML cured individuals, respectively, who did not produce IFN-gamma or IL-2 in vitro.ConclusionThis study shows that in spite of losing in vitro antigen-specific response to Leishmania, cured CL and ML subjects retain the ability to respond to SLA in vivo. These findings indicate that LST, rather than IFN-gamma production, may be a better assessment of lasting immunity to leishmaniasis in human studies, and thus a better tool for assessing immunization after vaccine. Furthermore, in cured individuals which maintains Leishmania-specific IFN-gamma production, effector memory CD4+ T cells were the main source of this cytokine.

Diminished Memory T-Cell Expansion Due to Delayed Kinetics of Antigen Expression by Lentivectors

Memory CD8+ T lymphocytes play a central role in protective immunity. In attempt to increase the frequencies of memory CD8+ T cells, repeated immunizations with viral vectors are regularly explored. Lentivectors have emerged as a powerful vaccine modality with relatively low pre-existing and anti-vector immunity, thus, thought to be ideal for boosting memory T cells. Nevertheless, we found that lentivectors elicited diminished secondary T-cell responses that did not exceed those obtained by priming. This was not due to the presence of anti-vector immunity, as limited secondary responses were also observed following heterologous prime-boost immunizations. By dissecting the mechanisms involved in this process, we demonstrate that lentivectors trigger exceptionally slow kinetics of antigen expression, while optimal activation of lentivector-induced T cells relays on durable expression of the antigen. These qualities hamper secondary responses, since lentivector-encoded antigen is rapidly cleared by primary cytotoxic T cells that limit its presentation by dendritic cells. Indeed, blocking antigen clearance by cytotoxic T cells via FTY720 treatment, fully restored antigen presentation. Taken together, while low antigen expression is expected during secondary immunization with any vaccine vector, our results reveal that the intrinsic delayed expression kinetics of lentiviral-encoded antigen, further dampens secondary CD8+ T-cell expansion.

T-cell biology in aging, with a focus on lung disease.

T cells are essential for defending hosts against microorganisms and malignancy as well as for regulating the development of immune-mediated inflammatory diseases like autoimmunity. Alterations in T-cell immunity occur with aging, affecting the function and proportions of T-cell subsets. Probably, the most noticeable age-associated change in T-cell immunity is an alteration in the frequency of naive and memory CD4+ and CD8+ T cells. In fact, the frequency of naive CD4+ and CD8+ T cells decreases with aging, whereas the frequency of memory CD4+ and CD8+ T cells increases. Also, changes in T-cell proliferation, cytokine production, memory response, and cytotoxicity as well as in regulatory T-cell number and function have been reported with aging. Such alterations could contribute to the development of infections, malignancies, and inflammatory diseases that rise with aging. Of interest, T cells are closely involved in the development of inflammatory airway and lung diseases including asthma and chronic obstructive pulmonary disease, which are prevalent in the elderly people. In addition, T cells play a major role in defending host against influenza virus infection, a serious medical problem with high morbidity and mortality in the elderly people. Thus, it is conceivable that altered T-cell immunity may account in part for the development of such respiratory problems with aging. Here, we will review the recent advances in T-cell immunity and its alteration with aging and discuss the potential effects of such changes on the lung.

Effect of different induction strategies on effector, regulatory and memory lymphocyte sub-populations in clinical islet transplantation

This prospective study assessed lymphocyte subsets in the peripheral blood of 42 islet allograft recipients using flow cytometry from 2 weeks and up to 2 years post-transplantation. Subjects received daclizumab (n = 16), Thymoglobulin (n = 12) or alemtuzumab (n = 14). Alemtuzumab was associated with an early (within 1 month) and transient (up to 6 months) increase in the frequency of CD3(+) CD4(+) Foxp3(+) T cells, while daclizumab induced a near complete loss of these cells (P <or= 0.001). The frequency of memory CD4(+) T cells was increased following depleting immunosuppression induction with either Thymoglobulin or alemtuzumab (P <or= 0.05), but remained unchanged while using daclizumab. Alemtuzumab induction resulted in a significant loss of memory B lymphocytes when compared with the other induction groups (P <or= 0.001). While the clinical significance of these findings remains to be fully determined, the observed altered balance between effector, regulatory and memory cells suggests that the immune status of patients will be affected according to the induction strategy chosen.

Age-associated change in the frequency of memory CD4+ T cells impairs long term CD4+ T cell responses to influenza vaccine.

We investigated the relationship of memory CD4+ T cells with the evolution of influenza virus-specific CD4+ T cell responses in healthy young and elderly people. Elderly individuals had a similar frequency of CD69+CD4+ T cells producing IFN-gamma and TNF-alpha at 1 wk, but a lower frequency of these CD4+ T cells at 3 mo after influenza vaccination. Although the elderly had a higher frequency of central memory (CM; CCR7+CD45RA-) CD4+ T cells, they had a significantly lower frequency of effector memory (EM; CCR7-CD45RA-) CD4+ T cells, and the frequency of the latter memory CD4+ T cells positively correlated with the frequency of influenza virus-specific CD69+CD4+ T cells producing IFN-gamma at 3 mo. These findings indicate that the elderly have an altered balance of memory CD4+ T cells, which potentially affects long term CD4+ T cell responses to the influenza vaccine. Compared with the young, the elderly had decreased serum IL-7 levels that positively correlated with the frequency of EM cells, which suggests a relation between IL-7 and decreased EM cells. Thus, although the healthy elderly mount a level of CD4+ T cell responses after vaccination comparable to that observed in younger individuals, they fail to maintain or expand these responses. This failure probably stems from the alteration in the frequency of CM and EM CD4+ T cells in the elderly that is related to alteration in IL-7 levels. These findings raise an important clinical question about whether the vaccination strategy in the elderly should be modified to improve cellular immune responses.

Proliferation responses to HIVp24 during antiretroviral therapy do not reflect improved immune phenotype or function.

To ascertain whether lymphoproliferation (LP) responses to HIVp24 in chronically infected patients treated with antiretroviral therapy (ART) predict an improved cytolytic T-cell phenotype or better in vivo immune function as measured by immunization responses. HIV-infected patients who started ART during chronic infection and who achieved viral suppression (HIV-RNA < 400 copies/ml for > 12 months) were grouped by the presence of strong [stimulation index (SI) > 10; n = 21] or absent (SI < 3; n = 18) LP to HIV-core antigen. The two groups were compared for functional immune responses to vaccination with diphtheria-toxoid, tetanus-toxoid and keyhole-limpet-hemocyanin, frequency of circulating naive and memory CD4+ and CD8+ T lymphocytes, maturation phenotype and expression of cytolytic molecules on total and HIV-specific CD8+ T cells, and frequency of memory CD4+ T cells with intracellular HIV-mRNA. Group comparisons were analyzed by non-parametric Mann-Whitney tests. Proportions were estimated by Pearson's chi analysis. There were no differences between the groups in immune responses to vaccination or in the numbers or phenotype of circulating T cells. In a subgroup of HLA-A2+ or B8+ patients, HIV-reactive CD8+ T cells in both groups had similar expression of perforin, granzyme A and T-cell maturation markers (CD27, CD28, CCR7, CD62L). However, patients with SI > 10 in response to HIVp24 tended to more often have high levels of circulating CD4+ T cells with intracellular HIV-1 mRNA than did patients with SI < 3. Following long-standing suppression of viral replication on ART, the presence of HIV-1 specific T-helper proliferation responses does not correlate with improved indices of immune phenotype or function but may reflect relatively higher levels of HIV-expression.

Developmental Changes and Functional Properties of Human Memory T Cell Subpopulations Defined by CD60 Expression

The present study was undertaken to examine developmental changes of T cells expressing CD60 and their functional properties. Three-color immunofluorescence analysis revealed that the CD60 antigen was preferentially expressed on a proportion of memory (CD45RO+) CD4+T cells, but less on memory CD8+T cells, while this antigen is undetectable in naive (CD45RO−) T cells. A frequency of memory CD4+T cells expressing CD60 in the peripheral blood was negligible in newborns and gradually increased with advancing age. CD60+memory CD4+T cells showed stronger proliferative responses to PPD and produced higher levels of IL-4 and IL-10 than CD60−ones, whereas production of IL-2 and IFN-γ was similarly found in both cell subpopulations. In addition, it was shown that efficient helper activity for Ig production by B cells was predominated in CD60+memory CD4+T cells. These results suggest that CD60 may be primarily expressed on the functionally differentiated memory effector cells among circulating CD45RO+CD4+T cells.