scholarly journals Comparative evaluation of memory T cells in COVID-19 patients and the predictive role of CD4+CD8+ double positive T lymphocytes as a new marker

2020 ◽  
Vol 66 (12) ◽  
pp. 1666-1672
Author(s):  
Yasin Kalpakci ◽  
Tuba Hacibekiroglu ◽  
Gulay Trak ◽  
Cengiz Karacaer ◽  
Taner Demirci ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Disease Severity ◽  
Cd4 T Cells ◽  
Memory T Cells ◽  
Severe Disease ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Double Positive ◽  
Memory Cd4 T Cells

SUMMARY BACKGROUND: The COVID-19 pandemic has affected the entire world, posing a serious threat to human health. T cells play a critical role in the cellular immune response against viral infections. We aimed to reveal the relationship between T cell subsets and disease severity. METHODS: 40 COVID-19 patients were randomly recruited in this cross-sectional study. All cases were confirmed by quantitative RT-PCR. Patients were divided into two equivalent groups, one severe and one nonsevere. Clinical, laboratory and flow cytometric data were obtained from both clinical groups and compared. RESULTS: Lymphocyte subsets, CD4+ and CD8+ T cells, memory CD4+ T cells, memory CD8+ T cells, naive CD4+ T cells, effector memory CD4+ T cells, central memory CD4+ T cells, and CD3+CD4+ CD25+ T cells were significantly lower in severe patients. The naive T cell/CD4 + EM T cell ratio, which is an indicator of the differentiation from naive T cells to memory cells, was relatively reduced in severe disease. Peripheral CD4+CD8+ double-positive T cells were notably lower in severe presentations of the disease (median DP T cells 11.12 µL vs 1.95 µL; p< 0.001). CONCLUSIONS: As disease severity increases in COVID-19 infection, the number of T cell subsets decreases significantly. Suppression of differentiation from naive T cells to effector memory T cells is the result of severe impairment in adaptive immune functions. Peripheral CD4+CD8+ double-positive T cells were significantly reduced in severe disease presentations and may be a useful marker to predict disease severity.

Ex Vivo Fludarabine Selectively Depletes Human Naive T-Cell Subsets: A Step Toward Modifying Donor Lymphocyte Infusion.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1071-1071
Author(s):  
Melody M. Smith ◽  
Cynthia R. Giver ◽  
Edmund K. Waller ◽  
Christopher R. Flowers
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cd4 T Cells ◽  
Memory T Cells ◽  
Ex Vivo ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Naïve T Cell ◽  
Naive T Cell

Abstract Ex vivo modification of donor lymphocytes with purine analogs (mDL) may help to minimize graft versus host disease (GvHD) while providing beneficial graft versus leukemia (GvL) effects. In a murine model system, we have shown that allogeneic donor splenocytes, treated with fludarabine ex vivo have significantly reduced GvHD activity when transferred to irradiated recipient mice, and retain anti-viral and GvL activities (Giver, 2003). This effect appears to be mediated by relative depletion of donor CD4 CD44low, “naive” T-cells. As a first step toward developing mDL for use in patients, we sought to evaluate the effects of ex vivo fludarabine exposure on human T-cell subsets, and to determine the minimum dose of fludarabine required to achieve this effect. Methods: Peripheral blood mononuclear cell samples from 6 healthy volunteers were evaluated at 0, 24, 48, and 72 hour time points after ex vivo incubation in varying dosages of fludarabine: 2, 5, and 10(n=3) mcg/ml. Fludarabine incubated samples were compared to samples that received no fludarabine (untreated). The total viable cell number was determined and the fractions and absolute numbers of viable CD4 and CD8 naïve and memory T-cells were determined using flow cytometry after incubation with 7-AAD (dead cell stain), CD4, CD8, CD45RA, CD62L, and CCR7 antibodies, and measuring the total viable cells/ml. Results: The numbers of viable CD4 and CD8 T-cells remained relatively stable in control cultures. Without fludarabine, the average viability at 72 hr of naive and memory T-cells were 92% and 77% for CD4 and 86% and 63% for CD 8 (Fig. 1A). Naive CD4 T-cells were more sensitive to fludarabine-induced death than memory CD4 cells. At 72 hr, the average viability of fludarabine-treated naive CD4 T-cells was 33% at 2 mcg/ml (8.2X the reduction observed in untreated cells) and 30% at 5 mcg/ml, while memory CD4 T-cells averaged 47% viability at 2 mcg/ml (2.3X the reduction observed in untreated cells) (Fig. 1B) and 38% at 5 mcg/ml. The average viability of naive CD8 T-cells at 72 hr was 27% at 2 mcg/ml and 20% at 5 mcg/ml, while memory CD8 T-cell viability was 22% at 2 mcg/ml and 17% at 5 mcg/ml. Analyses on central memory, effector memory, and Temra T-cells, and B-cell and dendritic cell subsets are ongoing. The 5 and 10 mcg/ml doses also yielded similar results in 3 initial subjects, suggesting that 2 mcg/ml or a lower dose of fludarabine is sufficient to achieve relative depletion of the naive T-cell subset. Conclusions: Future work will determine the minimal dose of fludarabine to achieve this effect, test the feasibility of using ex vivo nucleoside analog incubation to reduce alloreactivity in samples from patient/donor pairs, and determine the maximum tolerated dose of mDL in a phase 1 clinical trial with patients at high risk for relapse and infectious complications following allogeneic transplantation. Figure Figure

scholarly journals 343. T-cell Subsets Associated with Diabetes in Veterans with and without HIV

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S182-S183
Author(s):  
Samuel Bailin ◽  
Kathleen McGinnis ◽  
Wyatt J McDonnell ◽  
Kaku So-Armah ◽  
Melissa Wellons ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Immune Activation ◽  
Cd4 T Cells ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Hiv Status ◽  
Adaptive Immune ◽  
Memory Cd4 T Cells

Abstract Background Depletion of naïve CD4+ T cells and elevated adaptive immune activation are hallmarks of HIV infection. Higher proportions of memory CD4+ T cells are associated with prevalent diabetes in the general population, but few studies of persons with HIV (PWH) exist. Methods We analyzed data from 1532 PWH and 836 uninfected veterans in the longitudinal Veterans Aging Cohort Study (VACS), which archived peripheral mononuclear cells from these veterans between 2005 and 2007. We used flow cytometry to phenotype CD4+ and CD8+ T cells, including naïve, activated CD38+, senescent CD57+, total memory, and memory subsets. Prevalent diabetes (at blood collection) was identified in the VA electronic medical record using random glucose, hemoglobin A1c, ICD-9 codes, and medication. Cases were validated by two-physician chart review. We used multivariate logistic regression models adjusted for age, gender, body mass index, race/ethnicity, unhealthy alcohol use, hepatitis C, CMV status, and viral suppression stratified by HIV status to identify T-cell subsets associated with diabetes in PWH and uninfected. Results The cohort was 95% male, 68% African-American, and 22% diabetic. Higher CD4+CD45RO+ memory T cells were associated with prevalent diabetes in the uninfected and in PWH (P = 0.03 and P = 0.07, respectively; Figure A). Among subsets, diabetes was associated with higher transitional memory CD4+ T cells in the uninfected (P = 0.01), but higher central memory cells (P = 0.02) and lower effector memory cells (P = 0.04) in PWH. T effector memory RA+ cells were not associated with diabetes. Lower senescent CD4+CD57+ T cells were associated with diabetes in both PWH and uninfected (P = 0.03 and P = 0.04, respectively; Figure B), but results for naïve CD8+ T cells diverged: diabetes was associated with higher naïve CD8+cells in PWH but lower in uninfected (P = 0.01 and P &lt; 0.01, respectively; Figure C). We assessed interaction by HIV status in a pooled model, which was only significant for the naïve CD8+ T cells (P = 0.01). Conclusion The adaptive immune profile associated with prevalent diabetes was similar by HIV status and characterized by a shift in CD4+ T cells from senescent to memory phenotypes, suggesting that chronic immune activation contributes to the higher risk of diabetes in PWH. Disclosures All authors: No reported disclosures.

scholarly journals CD8+CD44hi but not CD4+CD44hi memory T cells mediate potent graft antilymphoma activity without GVHD

Blood ◽  
2011 ◽  
Vol 117 (11) ◽  
pp. 3230-3239 ◽  
Author(s):  
Suparna Dutt ◽  
Jeanette Baker ◽  
Holbrook E. Kohrt ◽  
Neeraja Kambham ◽  
Mrinmoy Sanyal ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Cd4 T Cells ◽  
Memory T Cells ◽  
Cell Subset ◽  
B Cell Lymphoma ◽  
Effector Memory ◽  
T Cell Subset ◽  
Progressive Growth

Abstract Allogeneic hematopoietic cell transplantation can be curative in patients with leukemia and lymphoma. However, progressive growth of malignant cells, relapse after transplantation, and graft-versus-host disease (GVHD) remain important problems. The goal of the current murine study was to select a freshly isolated donor T-cell subset for infusion that separates antilymphoma activity from GVHD, and to determine whether the selected subset could effectively prevent or treat progressive growth of a naturally occurring B-cell lymphoma (BCL1) without GVHD after recipients were given T cell–depleted bone marrow transplantations from major histocompatibility complex–mismatched donors. Lethal GVHD was observed when total T cells, naive CD4+ T cells, or naive CD8+ T cells were used. Memory CD4+CD44hi and CD8+CD44hi T cells containing both central and effector memory cells did not induce lethal GVHD, but only memory CD8+ T cells had potent antilymphoma activity and promoted complete chimerism. Infusion of CD8+ memory T cells after transplantation was able to eradicate the BCL1 lymphoma even after progressive growth without inducing severe GVHD. In conclusion, the memory CD8+ T-cell subset separated graft antilymphoma activity from GVHD more effectively than naive T cells, memory CD4+ T cells, or memory total T cells.

scholarly journals ID:3002 Notch-mediated control of memory T cells against cancer cells

2017 ◽  
Vol 4 (S) ◽  
pp. 12
Author(s):  
Koji Yasutomo
Keyword(s):  
T Cells ◽  
T Cell ◽  
Notch Signaling ◽  
Cancer Cells ◽  
Cd4 T Cells ◽  
Memory T Cells ◽  
Term Survival ◽  
Long Term Survival ◽  
Memory Cd4 T Cells

T cells recognize an antigen presented by self-MHC, and the part of initially activated T cells differentiate toward memory T cells. T cells also recognize cancer cells leading to generation of memory T cells against cancer-derived antigens although the activity of T cells are frequently suppressed by various factors. The release from T cell inhibitory factors could allow T cells to respond to cancer cells. However, it remains unclear which molecules are required for long-term survival of memory T cells and generation of memory T cells against cancer cells. Notch functions as a regulator for fate decision, activation and survival of immune cells. We have demonstrated the roles of Notch in mature T cell differentiation and found that Notch signaling is essential for the maintenance of memory CD4 T cells. The inhibition of Notch disturbs the survival of memory CD4 T cells. The effect of Notch on T cell survival depended on glucose uptake through cell surface Glut1 expression. We revealed that Notch is crucial for the long-term survival of memory T cells against cancer cells and suppression of Notch signaling reduced the tumor antigen-specific killing of cancer cells. Those data demonstrate that Notch is pivotal for the maintenance of memory T cells against cancer cells and suggest that activation of Notch signaling might be advantageous to cancer immunotherapy.

scholarly journals Interplay between IL-10, IFN-γ, IL-17A and PD-1 Expressing EBNA1-Specific CD4+ and CD8+ T Cell Responses in the Etiologic Pathway to Endemic Burkitt Lymphoma

Cancers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 5375
Author(s):  
Catherine S. Forconi ◽  
David H. Mulama ◽  
Priya Saikumar Lakshmi ◽  
Joslyn Foley ◽  
Juliana A. Otieno ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Burkitt Lymphoma ◽  
Cd4 T Cells ◽  
Cd8 T Cell ◽  
T Cell Response ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Healthy Children ◽  
Ifn Γ

Children diagnosed with endemic Burkitt lymphoma (eBL) are deficient in interferon-γ (IFN-γ) responses to Epstein–Barr Nuclear Antigen1 (EBNA1), the viral protein that defines the latency I pattern in this B cell tumor. However, the contributions of immune-regulatory cytokines and phenotypes of the EBNA1-specific T cells have not been characterized for eBL. Using a bespoke flow cytometry assay we measured intracellular IFN-γ, IL-10, IL-17A expression and phenotyped CD4+ and CD8+ T cell effector memory subsets specific to EBNA1 for eBL patients compared to two groups of healthy children with divergent malaria exposures. In response to EBNA1 and a malaria antigen (PfSEA-1A), the three study groups exhibited strikingly different cytokine expression and T cell memory profiles. EBNA1-specific IFN-γ-producing CD4+ T cell response rates were lowest in eBL (40%) compared to children with high malaria (84%) and low malaria (66%) exposures (p < 0.0001 and p = 0.0004, respectively). However, eBL patients did not differ in CD8+ T cell response rates or the magnitude of IFN-γ expression. In contrast, eBL children were more likely to have EBNA1-specific CD4+ T cells expressing IL-10, and less likely to have polyfunctional IFN-γ+IL-10+ CD4+ T cells (p = 0.02). They were also more likely to have IFN-γ+IL-17A+, IFN-γ+ and IL-17A+ CD8+ T cell subsets compared to healthy children. Cytokine-producing T cell subsets were predominantly CD45RA+CCR7+ TNAIVE-LIKE cells, yet PD-1, a marker of persistent activation/exhaustion, was more highly expressed by the central memory (TCM) and effector memory (TEM) T cell subsets. In summary, our study suggests that IL-10 mediated immune regulation and depletion of IFN-γ+ EBNA1-specific CD4+ T cells are complementary mechanisms that contribute to impaired T cell cytotoxicity in eBL pathogenesis.

scholarly journals Tigit Expression Defines a Subset of Activated Treg Cells with Prognostic Relevance in Follicular Lymphoma

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 1590-1590 ◽  
Author(s):  
Zhi-Zhang Yang ◽  
Hyo Jin Kim ◽  
Shahrzad Jalali ◽  
Hongyan Wu ◽  
Tammy Price-Troska ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Follicular Lymphoma ◽  
Research Funding ◽  
Memory T Cells ◽  
Treg Cells ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Cell Numbers ◽  
Treg Subset

Abstract T cell Ig and ITIM domain (TIGIT) is an immune checkpoint molecule that is expressed on a variety of cell types including NK cells, effector and memory T cells, and Treg cells. Upon ligation with CD155, TIGIT delivers an inhibitory signal and negatively regulates anti-tumor responses. While important in normal T-cell biology, the pathological significance of TIGIT expression and function in the tumor microenvironment of the patients with follicular lymphoma (FL) is largely unknown. The present study sought to phenotypically and functionally characterize TIGIT+ T cell subsets in FL. While its expression is not detected on resting T cells in peripheral blood, we found that TIGIT is highly expressed on intratumoral T cells from FL. Treatment with cytokines such as IL-4 and TGF-β downregulated TIGIT expression on T cells. We found that TIGIT is predominantly expressed on effector memory T cells (TEM) with an activation/exhausted phenotype, and TIGIT+ T cells have higher expression levels of CD69 and PD-1 when compared to TIGIT- T cells. Functionally, TIGIT+ T cells displayed reduced capacity of cell proliferation and cytokine production (IFN-γ and IL-2). Using mass cytometry (CyTOF), we observed that TIGIT is abundantly expressed on some intratumoral Treg (CD4+CD25+Foxp3+) cells, while other Treg cells lack TIGIT expression in FL, forming two subsets of Treg cells: CD4+CD25+TIGIT+ and CD4+CD25+TIGIT-. These two subsets are phenotypically distinct in that CD25+TIGIT+ cells exhibited increased expression of activation/costimulatory markers such as CD69, CD27 and CD28 compared to CD25+TIGIT-, suggesting an activated Treg subset of CD25+TIGIT+ cells. This CD25+TIGIT+ subset had increased suppressive function and could more effectively inhibit activation and proliferation of CD8+ T cells than CD25+TIGIT- cells. Furthermore, we found that lymphoma B cells promoted the development of TIGIT-expressing T cells as TGF-β-mediated downregulation of TIGIT on T cells was inhibited when CD19+ lymphoma cells were present. Using a cohort of 31 FL patients, we found that intratumoral TIGIT-expressing T cells were associated with a favorable prognosis. Patients with TIGIT+ T cell numbers greater than 50% had better overall survival than patients with TIGIT+ T cell numbers less than 50%. Taken together, our results reveal a role of TIGIT in defining Treg cell subsets with different immune function and TIGIT expression may be useful in predicting patient outcome in FL. Disclosures Ansell: Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Seattle Genetics: Research Funding; Celldex: Research Funding; Regeneron: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Affimed: Research Funding; Merck & Co: Research Funding.

Allosensitized Memory CD4 T Cells Induce Chronic Graft Versus Host Disease.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 449-449 ◽  
Author(s):  
Suparna Dutt ◽  
Diane Tseng ◽  
Tracy I. George ◽  
Joerg Ermann ◽  
Yinping Liu ◽  
...  
Keyword(s):  
T Cells ◽  
Cd4 T Cells ◽  
Chronic Gvhd ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Mouse Bone Marrow ◽  
Memory Cells ◽  
Activation Markers ◽  
Effector Memory Cells ◽  
Memory Cd4 T Cells

Abstract It has been reported that naive CD4+CD62LhiCD44lo T cells induce severe GVHD in a complete MHC mismatched allogeneic model of mouse bone marrow transplantation (BMT), but that effector memory CD4+CD62LloCD44hi T cells obtained from normal donors do not induce GVHD. The lack of GVHD-inducing capacity of effector memory cells from unprimed donors may reflect their lack of previous exposure to host alloantigens. We tested this hypothesis in a complete MHC mismatched allogeneic model of BMT by comparing the ability of effector memory T cells obtained from untreated C57BL/6 donors and donors immunized against host BALB/C alloantigens to induce GVHD. C57BL/6 donors were immunized by injecting 50 x106 host BALB/C spleen cells i.p. and after one week with 10x 106 cells. Both the unprimed and alloantigen primed CD4+ T cells expressed similar levels of lymph node homing chemokine receptor CCR7, and activation markers like CD69 and CD25. We sorted naive (CD62LhiCD44lo) and effector memory (CD62LloCD44hi) CD4+ T cell subsets from C57BL/6 donor mice four weeks after immunization, and compared their alloreactivity to BALB/C in an in vitro MLR. Interestingly effector memory CD4+ T cells from primed mice produced significantly higher levels of IFNγ compared to the effector memory from unprimed donors. We found that CD62LloCD44hi cells from unimmunized donors failed to induce GVHD in 85% of the hosts over 100 days while CD62LloCD44hi cells from immunized donors caused progressive weight loss and death in 100% of hosts (p &lt;0.001). Whereas naive CD4+ T cells from unimmunized donors accumulated rapidly in the lymph nodes and spleen of irradiated hosts, effector memory CD4+ T cells had markedly reduced accumulation in these tissues. Furthermore, at day 6 after transplantation effector memory CD4+ T cells from primed mice, showed hundred fold higher accumulation in the host liver compared to unprimed effector memory donor CD4+ T cells. Long term surviving hosts transplanted with primed effector memory cells showed histopathological features of chronic GVHD in liver characterized by portal tract inflammation and lymphocyte infiltration with bile duct injury. In conclusion, memory CD4+ T cells from donors immunized to host alloantigens are able to induce chronic GVHD , but memory cells from unimmunized donors do not.

CXCR3 Is Required for the Efficient Recruitment of Bone Marrow-Resident Memory T Cells to Inflamed Tissues,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3242-3242
Author(s):  
Robbert van der Voort ◽  
Claudia Brandao ◽  
Thomas J. Volman ◽  
Viviènne Verweij ◽  
Klaas van Gisbergen ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Immune Responses ◽  
Cd8 T Cells ◽  
Memory T Cells ◽  
Central Memory ◽  
T Cell Subsets ◽  
Effector Memory ◽  
Memory T Cell

Abstract Abstract 3242 Although the importance of the bone marrow (BM) in hematopoiesis is well known, its function in adaptive immune responses has only recently been acknowledged. Currently it is known that the BM contains fully functional CD4+ and CD8+ T cells that can engage in both primary and secondary immune responses. Interestingly, most of these T cells belong to the memory T cell lineage, identifying the BM as one of the largest memory T cell reservoirs in the body. Since not much is known about the trafficking of BM T cells, we compared the homing phenotype and function of T cell subsets in the BM, blood, spleen and peripheral lymph nodes (pLN). In addition, we determined the expression of chemokine mRNA and protein levels in the BM and other lymphoid organs. We confirmed that at least 80% of the CD4+ and 60% of the CD8+ BM T cells have a memory phenotype, and that most CD4+ T cells belong to the effector memory lineage, while the CD8+ population predominantly consists of central memory T cells. Most BM T cells expressed the chemokine receptor CXCR3, the adhesion molecules P-selectin glycoprotein ligand 1 and VLA-4, and increased levels of CD44 and LFA-1, as compared to T cells from the spleen. In addition, L-selectin was absent from most CD4+ BM T cells, but present on virtually all CD8+ T cells. Notably, the percentage of CXCR3+ T cells within the effector memory and central memory subsets from BM was higher than within the same subsets from pLN. Furthermore, BM contained significant mRNA levels of the CXCR3 ligands CXCL9, CXCL10 and CXCL11. An in vivo migration assay using a mixture of fluorescent-labeled T cells from CXCR3-deficient mice and control mice indicated however that during homeostasis CXCR3 does not play a major role in BM entry or retention. These data suggest that CXCR3 expressed by memory T cells is rather involved in BM exit, than in BM entry. Indeed, we observed that, as compared to control mice, CXCR3−/− mice contained significantly more CD4+ and CD8+ T cells in their BM. Additional in vitro assays demonstrated that CD4+ and CD8+ BM T cells migrated vigorously in response to CXCL9 and CXCL10, generally released in high concentrations during inflammation. Finally, we demonstrate that CXCR3−/− effector/effector memory T cells, but not wild type T cells, accumulate in the BM of mice infected with lymphocytic choriomeningitis virus. Altogether, these data demonstrate that the BM is a major reservoir of memory T cells that employ CXCR3 to quickly respond to chemotactic signals from inflamed tissues. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Phenotypic and functional alteration of CD4+ T cells after antigen stimulation. Resolution of two populations of memory T cells that both secrete interleukin 4.

1989 ◽  
Vol 169 (6) ◽  
pp. 2245-2250 ◽  
Author(s):  
K Hayakawa ◽  
R R Hardy
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cd4 T Cells ◽  
Memory T Cells ◽  
T Cell Subsets ◽  
Interleukin 4 ◽  
Permanent Loss ◽  
Two Populations ◽  
Functional Alteration

Phenotypic and functional alteration of murine CD4+ T cells after antigenic stimulation was studied using two anti-T cell mAbs recently described that define four distinct T cell subsets. Activation of T cells resulted in the permanent loss of 3G11 expression. However, two phenotypically distinct memory T cell populations were established depending on the system used; whereas those for anti-KLH antibody response were enriched in the fraction expression 6C10 (Fr. III), memory T cells for the allogeneic MLR lacked such expression (Fr. IV). Furthermore, successive stimulation with antigen in vitro resulted in secretion of IL-4 without detectable IL-2. This alteration of phenotype and interleukin secretion was also demonstrable when starting with 3G11+6C10- cells (Fr. I), the fraction that secretes IL-2 exclusively upon activation.

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