Maturation of Lymphocyte Immunophenotypes and Memory T Helper Cell Differentiation During Development in Mice

The goal of this study was to systematically investigate the ontogeny of lymphoid populations throughout postnatal development. In CD-1 mice, peak lymphocyte numbers occurred in blood on postnatal day 10 (dl0) including those for natural killers (NK1.1), B cells (CD19), T helper (CD3CD4), naïve T helper (CD4CD62L^posCD44^low), memory T helper (CD4CD62L^negCD44^high), and T cytotoxic (CD3CD8) cells. As percent of total lymphocytes, peaks were achieved by d10 for all T helper subtypes but not B cells which declined to a nadir. In spleen, lymphocyte numbers increased exponentially after d10. Proportionately, NK and T cells peaked on d10, declined by d20, and increased 2–3-fold by d45. Naive T cells constituted the majority of lymphocytes during development while memory cells gained to 2.2% (blood) and 12 % (spleen) by d20. C57BL/6 mice had similar profiles except that the B cell nadir and T cell subset peaks were at d5. Peripheralization of critical numbers of lymphocytes by d10, and importantly, development of a repertoire of memory cells by d20, may define immune response capabilities that close the period of immaturity for the neonate.     

Aging and Lymphocyte Subsets in the Spleen and Peripheral Blood of the Sprague-Dawley Rat

This study was undertaken to determine the effects of aging on lymphocyte subsets in the peripheral blood and spleens of Sprague-Dawley rats. Rats aged 3, 13 and 26 months were used in the study. Analyses of dual labeled lymphocytes from the 26 month animals show decreases in the numbers of lymphocytes due to decreased cellularity (spleen) or reduced lymphocyte percentages within the total white blood cell population (peripheral blood). In the spleens and blood of the oldest rats, there were reduced numbers of Total T, T helper/ amplifier (T_h/a), virgin T_h, and natural killer (NK) cells. Other changes were observed in the spleen but not peripheral blood. The numbers of T cytotoxic/suppressor cells (T_c/s) B cells, “autoimmune” B cells and NK cells were reduced in the spleen but remained within normal limits in peripheral blood. The data show aging exerts different effects on the peripheral blood and splenic compartments of the immune system. These differences may have teleological significance in relation to immune responses to xenobiotics and neoplastic cells.     

Maternal modulation of neonatal immune system development

Changes in programming of neonatal immune development were effected through maternal immune modulation (Leishmania major inoculation). In progeny of these dams, immune profiles in both blood and spleen were changed throughout the neonatal period and were pronounced after weaning. White blood cell (WBC) and lymphocyte counts in blood of 45-day-old progeny were two-fold less than control animals. In blood, proportions of B cells were greater, while T helpers, Tc/s and NK cells were less than in controls. In contrast, proportions of splenic B and NK cells were greater than controls. But, proportions of all T and Tc/s cells on d20 and 45 were lower than controls. In blood, absolute numbers of all T, Th na?ve and Th memory cells were lower than in controls. In contrast, in the spleen, numbers of NK, T and Th naive and memory cells were up to 200% greater than in control pups. Cytokine responses of splenic lymphocytes stimulated through CD3 ligation revealed no difference in IL-4 production. In contrast, IL-2 and IFNgamma were lower on d45 and 5, respectively, in the experimental compared to control mice. These data support the hypothesis that maternal immune events during gestation can modulate the pattern of immune development in offspring.     

Natural killer cells and B lymphocytes in L-selectin and Mac-1/LFA-1 knockout mice: marker-dependent,but not cell lineage-dependent changes in the spleen and bone marrow

The majority of B lymphocytes, virgin T lymphocytes and a subpopulation of memory T cells express the addressin, L-selectin. Natural killer (NK) cells in rodents and humans also express L-selectin. We have shown that a similar proportion (40%) of NK cells in mouse spleen also express the integrin, CD18Mac-1, and moreover, that NK cells express both the addressin and the integrin constitutively. It was the aim of the present study to quantify, in knock-out mice deficient for either the L-selectin addressin, or the CD18:Mac-1/LFA-1 integrins, NK cells and B cells in both the spleen and their bone marrow birth site. These cells, in both organs, were immunophenotypically stained with FITC-conjugated anti-NK1.1 (to identify NK cells), and FITC-conjugated anti-mouse B220 (to identify B lymphocytes) and subjected to flow-cytometric analysis using a FACScan equipped with a doublet discrimination module. From the known total organ (spleen, femurs) cellularity, obtained by means of an electronic cell counter, at the time of extraction of each organ, the absolute numbers of NK cells and B lymphocytes from each mouse were obtained. The results revealed that there are significantly more NK cells and B lymphocytes in the spleens of CD18:Mac-1/LFA-1 knockout mice than in control (same strain) mice. Moreover, in L-selectin knockout mice spleens, NK cells and B lymphocytes were elevated by 26.2% and 17.8% respectively. NK cells and B lymphocytes in the bone marrow of the integrin knockout showed no difference from control, however, both cell types in the bone marrow of the L-selectin knockout mice fell to only 3/4 their control levels. Collectively, the results demonstrated that there are organ-specific, but not cell lineage-specific differences in the absolute numbers of NK cells and B lymphocytes, in integrin-deficient (CD18:Mac-1/LFA-1 knockout) mice and addressin-deficient (L-selectin knockout) mice.     

Relative and absolute numbers of T lymphocyte subpopulations and NK cells in male population in relation to age

Using BMA monoclonal antibodies and fluorescent microscope, percentages and absolute numbers of lymphocytes, T cell subsets and NK cells were enumerated in peripheral blood from 126 healthy men. Although absolute numbers of total lymphocytes did not differ according to age, the numbers and percentage of natural killer (NK) cells showed positive interrelationship with age. The percentage but not absolute numbers of cells reacting with BMA 030 (CD3) and BMA 040 (CD4) antibodies were significantly increased only in groups aged of 20-29 yrs and 30-39 yrs. The percentage and number helper/inducer T cells (CD4) were comparable in the four groups of subjects. These results indicate that peripheral lymphocyte populations and T cell subsets and NK cells remarkably vary in healthy men over a wide range of ages.     

Lymphocyte subsets in term and significantly preterm UK infants in the first year of life analysed by single platform flow cytometry

This observational study describes the ranges observed for lymphocyte subsets for significantly preterm infants (<32 weeks) in the first year of life, measured by single platform flow cytometry and compared to identically determined subsets in term infants. After ethical approval 39 term and 28 preterm infants had lymphocyte subset analysis before and after their primary immunization series. Median values with 5th and 95th percentiles of absolute counts and percentages are presented for total lymphocytes, T cells, NK cells, B cells, cytotoxic T cells, helper T cells, dual positive T cells, activated T cells, activated T helper cells (including T regulatory cells), pan memory T cells, pan naive T cells, memory helper T cells, naive helper T cells and the T helper/suppressor ratio. The lymphocyte profile of the preterm infants differed from that of the term infants.     

Development of lymphocyte subsets in tumor patients after subcutaneous administration of mistletoe extracts]

OBJECTIVE: In order to exclude the possibility that mistletoe therapy may result in immunosuppression, as indicated by a significant reduction of defined lymphocyte subsets, PATIENTS AND METHODS: peripheral blood cells of 23 tumour patients were treated subcutaneously with increasing concentrations of aqueous mistletoe extracts (Helixor(R)). Results and Conclusions:Within an observation period of 7 months, the relative amount of lymphocytes and the number of natural killer (NK) cells increased while the number of lymphocyte subsets (i. e. CD19+ B cells, CD4+ T helper cells, CD8+ CD28- suppressor cells, CD8+ CD28+ cytotoxic cells) and the proportion of CD25+ (activated) cells within T cells showed a statistically remarkable trend; due to the multiple test problem of statistical evaluation this trend is not allowed to be termed significant. The leucocytes decreased insignificantly within the observation period. However, we were unable to verify a suggested increase of defined lymphocyte subsets within 2-3 months after the onset of mistletoe treatment. Nevertheless, for the parameters CD19+ B cells, CD4+ T helper cells, CD8+ cells, CD8+ CD28+ cytotoxic cells and CD16+/CD56+ NK cells we observed statistically remarkable peaks within die 2nd and 3rd month of therapy, confirming the hypothesis. The responses to the extracts were obviously interindividually different; the immune responses especially of patients with a lower number of peripheral T cells were less significant as compared to those of patients with adequate T cell numbers. Surprisingly, even an increase of the drug concentration >3 ng mistletoe lectin (as determined within the whole plant extract) per kg body weight enhanced the number of CD4+ T helper cells. A decreased immunological reaction on mistletoe extracts was shown especially for patients with a reduced number of peripheral T cells, whereas patients with normal T-cell number were more reactive.     

Tumor-induced suppression of interferon-gamma production and enhancement of interleukin-10 production by natural killer (NK) cells: paralleled to CD4+ T cells

The predominance of type two cytokines in syngeneic B16 tumor-bearing mice was confirmed by analysing supernatant contents and mRNA copies of IFN-gamma, IL-4, IL-5, IL-10 and IL-13 from splenocytes. The cytokine-producing lymphocytes were then examined by double-staining flowcytometry. Both CD4+IFN-gamma+ T cells and DX5+IFN-gamma+ NK cells from spleen significantly declined, interestingly, the declining degrees of DX5+IFN-gamma+ NK cells were much greater than those of CD4+IFN-gamma+ T cells by the percentage in whole NK or T cells or the absolute amounts per spleen at early tumor stage (day 10) or tumor-advanced stage (day 20). In contrast to DX5+IFN-gamma+ NK cells, DX5+IL-10+ NK cells increased during tumor progression, the increasing degrees of DX5+IL-10+ NK cells were also much greater than those of CD4+IL-10+ T cells by the percentage or the absolute amounts. Though the percentage of DX5+IL-4+ NK cells only increased in early tumor stage (day 10), the increasing degree was also greater than that of CD4+IL-4+ T cells. In 20xfield view under laser confocal microscope, the mean numbers of DX5+IFN-gamma+ NK cells and CD4+IFN-gamma+ T cells dramatically declined after tumor inoculation. These results suggest that cytokines produced by NK cells, at least partly, account for the balance of type one and two cytokines as done by T cells, and in some conditions, that the NK1 or NK2 cells were possibly more sensitive to tumor progression.     

Normal mouse kidneys contain activated and CD3+CD4- CD8- double-negative T lymphocytes with a distinct TCR repertoire

Healthy liver, intestine, lung, and skin harbor resident lymphocytes with conventional and unconventional phenotypes. Lymphocytes also have been detected in healthy mice kidneys; however, these cells have not been well studied and have been largely overlooked. To better characterize the intra-renal lymphocytes, we extensively perfused C57BL/6J mice with PBS and then isolated mononuclear cells for flow cytometry analysis. We observed T cells, B cells, and NK cells in normal mice kidneys after extensive perfusion. Approximately 50% of kidney T lymphocytes expressed intermediate levels of CD3 (CD3int T cells). Similar to liver and lung, a high percentage of unconventional CD3+CD4(-)CD8(-) double-negative T cells was observed in normal mice kidneys, from which 11% expressed B220 antigen. Unlike the spleen and blood, the classic CD4+ and CD8+ T lymphocytes in the kidney had a high proportion of activated CD69+ and effector/memory CD44- CD62L ligand phenotypes. Also, a small percentage of CD4+CD25+forkhead box p3+ and NKT cells was observed in perfused and exanguinated kidneys. In addition, a distinct TCR repertoire was found on intra-renal conventional and unconventional T cells compared with those from the spleen. Finally, after 24 h of renal ischemia reperfusion injury (IRI), increased production of cytokines IFN-gamma and TNF-alpha by CD4+ and CD8+ T cells, isolated from perfused kidneys, was observed. These data suggest that some of these cells harbored in the kidney could be implicated in the immune response of the IRI pathogenic process.     

Immunological changes in young and old adults during brief laboratory stress

Few data are available on the response of the human immune system to acute psychological stressors under controlled laboratory conditions. Young female subjects (21-41 years) showed increases in natural killer (NK) cell activity, and in the numbers of circulating CD8 suppressor/cytotoxic T cells, and natural killer lymphocytes following a brief (12 minute) stressful mental arithmetic examination. Older female subjects (65-85 years) failed to show the stress-related increase in NK activity. The psychological stress did lead to increases in the numbers of circulating CD8 suppressor/cytotoxic T cells and NK lymphocytes in old subjects to a similar degree as that seen in the young group. No changes in the numbers of helper/inducer T cells (CD4), total T cells (CD3), or B cells (CD20) were found following the stressor for either group. Cardiovascular, catecholamine, and subjective stress responses were similar for the two age groups. These results demonstrate that brief psychological stress is associated with some rapid immune cell changes, including release of CD8 suppressor/cytotoxic T cells and NK cells into circulation, and in young subjects, increases in NK activity. The absence of an NK activity increase in the older subjects indicates that NK cell mobilization and cell lysis induced by NK cells may be differentially affected by stress. The results also suggest the possibility of an age-related deficit in the up-regulation of NK activity under some environmental demands.     

Lymphocyte membrane antigen expression and intracellular cytokine patterns in an asymptomatic patient with persistently high serum levels of IgE.

BACKGROUND: Patients completely asymptomatic with extremely high levels of IgE have rarely been reported. One such case, in which the immunophenotype pattern of lymphocyte subsets and their cytokine profile were investigated, is described here. OBJECTIVE: To assess whether the cytokine production was consistent with a T helper 2-type immune response, as suggested by theories regarding the functional polarization of helper and cytotoxic T cells in hyper-IgE conditions. METHODS: An asymptomatic 79-year-old man presented with persistent high levels of serum IgE and sporadic hypereosinophilia without any evidence of an underlying pathologic condition. We investigated the immunophenotype of circulating lymphocytes, the expression/release of CD30 (a member of the tumor necrosis factor receptor family preferentially associated with T helper 2-type immune responses) and the intracellular patterns of interferon-gamma (IFN-gamma), Interleukin-2 (IL-2), IL-4, IL-5, and IL-10 production by T cell subsets, as evaluated by single-cell flow-cytometric analysis. RESULTS: The majority of lymphocytes displayed the membrane immunophenotype of NK cells. Both CD4+ and CD8+ T cells were reduced and expressed the "memory" (CD4+/CD45RO+) and the "naive" (CD8+/CD45RA+) phenotypes, respectively. Among CD4+ T cells, CD30 expression was increased in the resting condition and was further inducible following stimulation with mitogenic anti-CD3. Interleukin-4, IL-2, and IL-10 production by CD4+ T cells was increased, whereas IFN-gamma was reduced as compared with normals. CONCLUSIONS: The data suggest that a polarization of CD4+ T cells towards a T helper 0/2-type cytokine pattern occurred in this patient in spite of CD4+ cell reduction and NK cell expansion.     

The role of donor T cells for target organ injuries in acute and chronic graft-versus-host disease

Donor T cells are crucial for target organ injury in graft-versus-host disease (GVHD). We examined the effects of donor T cells on the target organs using a parent-into-F1 model of acute and chronic GVHD. Donor T cells showed engraftment in the spleen, small intestine and liver of mice with acute GVHD, causing typical GVHD pathology in these organs. Interferon-gamma and Fas ligand expression were up-regulated, and host lymphocytes were depleted in the target organs of these mice. In contrast, donor T cells did not show engraftment in the small intestine of mice with chronic GVHD, and no GVHD pathology was observed in this organ. However, both donor T-cell engraftment and GVHD pathology were observed in the spleen and liver of chronic GVHD mice, along with the up-regulation of interleukin-4 (IL-4) and IL-10 expression plus the expansion of host lymphocytes such as splenic B cells and hepatic natural killer (NK) 1.1+ T cells. Donor anti-host cytotoxic T-lymphocyte activity was observed in spleen cells from mice with acute GVHD, but not in spleen cells from mice with chronic GVHD. Transplantation of Fas ligand-deficient (gld) spleen cells did not induce host lymphocyte depletion in target organs. These results indicate that donor T cells augment type 1 T helper immune responses and deplete the host lymphocytes from target organs mainly by Fas-mediated pathways in acute GVHD, while donor T cells augment type 2 T helper immune responses and expand host splenic B cells and hepatic NK1.1+ T cells in chronic GVHD.     

小鼠脾脏淋巴细胞体外培养前后细胞表面标记物CD3、CD4、CD44、CD62L 的变化

目的:探讨体外培养小鼠脾脏淋巴细胞后,细胞表面标记物CD3、CD4、CD44、CD62L 的变化。方法:用淋巴细胞分离液分离小鼠脾脏淋巴细胞,37益细胞孵箱中体外培养3 d 后,向细胞中加入流式抗体Mouse CD3e PE-CY7、Mouse CD4 FITC、Mouse CD44 PE、Mouse CD62L APC,同时设阴性对照,应用流式细胞仪检测细胞表面标记物CD3、CD4、CD44、CD62L 的水平。结果:小鼠脾脏淋巴细胞分离后直接做流式检测,CD3+ CD4+细胞占19.09%,其中98.61% 的细胞为CD44+ ,68.71% 为CD62L+ 。体外培养后CD3+ CD4+细胞占8.96%,其中71.82%为CD44+ ,11.27%为CD62L+ 。哮喘小鼠脾脏淋巴细胞分离后直接做流式检测,CD3+ CD4+ 细胞占20.33%,其中97.72% 的细胞为CD44+ ,75.74% 为CD62L+ 。体外培养后CD3+ CD4+ 细胞占7.2%,CD44 阳性细胞占58.21%,CD62L 阳性细胞仅占2.77%。结论:小鼠脾脏淋巴细胞体外培养后,细胞表面标记物CD44和CD62L 发生巨大变化,CD62L 呈现明显下调趋势,接近消失,CD44 也有下调。     

Changes in T,B, and NK Lymphocyte Subsets During and After Normal Pregnancy

PROBLEM: Pregnancy affects the maternal immune system and the clinical course of maternal diseases. Here we report the changes in the detailed lymphocyte subsets of helper T cells, suppressor T cells, CD5⁺ B cells, T cell receptor (TCR) αβ-positive T cells (Tαβ cells), TCRαβ-negative T cell (Tγδ cells), and others during and after pregnancy through to one year postpartum, and discuss the significance of the changes. METHOD: The absolute numbers of helper T cells, suppressor T cells, cytotoxic T cells, TCRαβ-negative T cells (Tγδ cells), CD5^— B cells, CD5⁺ B cells, and NK cell subsets were examined by two-color flow cytometry in peripheral blood from 51 healthy non-pregnant women, 106 healthy pregnant women, and 148 healthy postpartum women. RESULTS: In early pregnancy, the numbers of suppressor T cells and NK cells with strong cytotoxicity (NK⁺⁺⁺ cells) increased, and the number of cytotoxic T cells decreased. In late pregnancy, the helper T cell and NK⁺⁺⁺ cell numbers decreased. Tαβ, CD5^— B and CD5⁺ B cells decreased during pregnancy. After delivery, helper T cells and cytotoxic T cells increased from 1 to 4 months postpartum, and suppressor T cells increased at 7 months postpartum. TCRαβ-negative T cells increased at 4 to 10 months postpartum. Both CD5^— and CD5⁺ B cells decreased further at 1 month postpartum, but CD5⁺ B cells increased markedly at 7 to 10 months postpartum. CONCLUSIONS: These data indicate that 1) early increases of suppressor T cells and NK⁺⁺⁺ cells during pregnancy may be related to the mechanism to accept or reject the fetus in early pregnancy, respectively; 2) late decreases of helper T cells and NK⁺⁺⁺ cells may be related to the maintenance of pregnancy: 3) postpartum increases of helper T cells, cytotoxic T cells, TCRαβ-negative T cells (Tγδ cells), and CD5⁺ B cells may be related to the postpartum aggravation of autoimmune diseases; and 4) the immunological effects of pregnancy remains until about 1 year after delivery.     

Psychological stress during exercise: Lymphocyte subset redistribution in firefighters

The purpose of this study examined the changes in heart rate (HR), catecholamines (NE, EPI) and percentages of blood lymphocyte subsets (CD3+ T cells, CD3+ CD4+ helper T cells, CD3+ CD8+ cytotoxic T cells, CD3− CD56+ NK cells, CD4/CD8 ratio, CD19+ B cells, and total lymphocytes [NK cells+ T cells+ B cells]) in firefighters exposed to a computerized firefighting strategies and tactics decision-making challenge while participating in moderate intensity exercise. Furthermore, this study also examined the possible relationships between catecholamines (NE and EPI) and blood lymphocyte subsets following combined mental and physical challenge. Ten professional male firefighters participated in two counterbalanced exercise conditions on a cycle ergometer: (1) 37 min of cycle ergometry at 60% VO_2max (exercise alone condition; EAC) and (2) 37 min of cycle ergometry at 60% VO_2max along with 20 min of a computerized firefighting strategies and tactics decision-making challenge (firefighting strategies condition; FSC). FSC elicited significantly greater HR, NE, and EPI when compared to EAC. Both EAC and FSC elicited increases in CD3− CD56+ NK cells. The percentages of CD3+ T cells, CD3+ CD4+ helper T cells, CD4/CD8 ratio, CD19+ B cells, and total lymphocytes were lower immediately following both conditions. Following dual challenge NE AUC was negatively correlated with percentage of CD19+ B cells immediately post challenge, and HR was negatively associated with the percent change in the CD4/CD8 ratio from pre to post challenge. These elevations in NE and heart rate simultaneously in response to the dual challenge suggest greater sympathetic activation that in turn would possibly explain the alteration in the distribution of lymphocyte subsets.     

Characterization of CD4+ T cells in mouse bone marrow. I. Increased activated/memory phenotype and altered TCR Vbeta repertoire

A significant proportion of memory B cells home to bone marrow (BM) which is a major site of anamnestic antibody responses in mice. We hypothesized that memory T cells likewise accumulate in BM perhaps to provide help for antibody production, and that the compartment of CD4+ T cells in BM of unimmunized mice would be enriched for memory phenotype cells that might have been activated by environmental antigens. The phenotype of activated/memory CD4+ lymphocytes has been defined as CD44hi CD45RBlo CD62L-. Conversely, the phenotype of immunologically naive cells is CD44lo CD45RBhi CD62L+. Flow cytrometric analysis of tissue from normal, adult C57BL/6 mice identified 1-2 % CD3+CD4+ cells in BM. Up to 40 % of CD3+CD4+ cells in the BM expressed the activated/memory phenotype compared with < or = 10% in the spleen and lymph nodes. Analysis of TCR Vbeta repertoire revealed that expression of Vbeta3 and Vbeta7 genes was increased as much as fourfold in BM compared to the periphery; most of this increase was within the CD44hi T cells. The accumulation of activated/memory T cells and clonotypic expansion(s) was not seen in the BM of germ-free mice, indicating that it reflects the history of the animal's exposure to antigens. Finally, immunization of mice which express a transgenic T cell receptor specific for ovalbumin peptide resulted in appearance of antigen-specific T cells with activated/memory phenotype in the BM.     

Differential Adhesion Molecule Expression on Porcine Mononuclear Cell Populations

Adhesion molecule expression was analysed on porcine blood and lymphoid organ CD4⁺ CD8^? naïve T helper (Th) lymphocytes, CD4⁺ CD8⁺ memory Th lymphocytes (particular to the pig), CD4^? CD8^high cytotoxic T (Tc) lymphocytes, CD4^? CD8^low NK cells (CD3^? in the pig), CD4^? CD8^? T-cell receptor-γδ-positive (TCRγδ⁺) lymphocytes, B lymphocytes and monocytes. While CD44 expression was relatively homogeneous amongst mononuclear cells, differences were noted for the integrins. Blood naïve Th lymphocytes were CD49d^low CD11a^low, as were splenic naïve Th cells; blood memory Th lymphocytes were CD49d^high CD11a^low, splenic memory Th cells were CD49d^high CD11a^high with a CD49d^high CD11a^low subpopulation; blood Tc lymphocytes were mainly CD49d^low CD11a^low, and splenic cells were CD49d^high CD11a^high. Lymph node lymphocytes were more homogeneous in their integrin expression. These were relatively CD49d^low CD11a^low, except the memory Th lymphocytes which had higher integrin expression. B lymphocytes related to the majority of integrin^low T cells, while monocytes and NK cells were CD49d^high CD11a^high; γδ T lymphocytes showed variable CD49d expression but a CD11a^high phenotype. CD49d^high CD11a^high co-expression was found, and this phenotype was typical of, but not exclusive to, CD25⁺ (activated) lymphocytes. These results demonstrated that porcine memory Th lymphocytes and NK cells, as well as activated cells, would have increased integrin-dependent activities compared with naïve Th lymphocytes, and integrin-dependent reactions would probably vary between blood and lymphoid organ cells.     

Most parasite-specific CD8+ cells in Trypanosoma cruzi-infected chronic mice are down-regulated for T-cell receptor-alphabeta and CD8 molecules

The present study shows that CD8+ T lymphocytes expressing low levels of T-cell receptor (TCR)alphabeta, CD8 and CD3 accumulate in the spleen, blood, peritoneum and liver, but not in the lymph nodes of mice chronically infected with Trypanosoma cruzi. Analysis of spleen lymphocytes reveals that most CD8LOW TCRLOW T cells have an experienced phenotype (CD44HIGH CD62LLOW and CD45RA,B,CLOW). These cells have small size, lack activation markers such as CD69, CD25 and CD11b (Mac-1), and do not spontaneously secrete cytokines, suggesting they are at the resting state. When stimulated in vitro with T. cruzi-infected macrophages, TCRLOW CD8LOW T cells behave as parasite-specific memory cells, readily responding with interferon-gamma (IFN-gamma) production. Indeed, among parasite-activated CD8+ lymphocytes, IFN-gamma production was mostly due to TCRLOW CD8LOW cells. Upon in vitro stimulation with anti-CD3/CD28 monoclonal antibodies, down-regulated cells produce IFN-gamma and tumour necrosis factor-alpha, but not interleukin IL-10 or IL-4. Our results indicate that despite parasite persistence, most T. cruzi-specific experienced CD8+ cells are resting. Nevertheless, when encountering infected macrophages these cells differentiate to Tc1 effectors.     

Dynamics of CD62L/CD45RB CD4+ and CD8+ lymphocyte subsets in hepatic and splenic tissues during murine visceral leishmaniasis

This study aimed to characterise, for the first time, the dynamics of CD4+ and CD8+ lymphocyte CD62L/CD45RB subsets, during visceral leishmaniasis. Memory/activated status of hepatic and splenic T cells was compared in mice strains with "cure" and "non-cure" phenotypes to Leishmania infantum infection. In both mice strains, a correlation between the dynamics of the memory CD4+ and CD8+ T cells (CD62Llow/CD45RBlow) subsets in the liver and the pre-activated phenotype of lymphocytes (CD62Llow/CD45RBhigh) from the spleen was detected suggesting that this organ is the source of Leishmania-specific T lymphocytes that migrate to the liver, where parasite replication is highly active. In the liver, these pre-activated cells become effector T lymphocytes, however, a strong regulation of CD8+ T cell effector function was observed, probably preventing hepatic tissue damage. Comparing mice strains with "cure" and "non-cure" phenotype, an imbalance between "protective" CD45RBhigh and "pathogenic" CD45RBlow CD4+ subsets in B10.D2/n animals might be involved in the evolution of a non-healing infection.     

Alterations of Lymphocyte Populations in Lymph Nodes But Not in Spleen During the Latency Period of Adjuvant Arthritis

The aim of this study was to analyze potential imbalances in lymphocyte populations from regional lymph nodes (LN) and spleen occurring before the development of the outer inflammation of adjuvant arthritis (AA). Percentages and absolute numbers of CD5⁺, CD4⁺, CD8⁺, Ig⁺, I-A⁺, NKR-P1⁺ and TCR⁺ cells were determined. No differences in percentages of T or NK cells were found either in LN or spleen, thus ruling out an important role of these minor subpopulations in these early stages of AA. While no significant lymphocyte imbalances were observed in spleen, an increase in the percentage of B lymphocytes was found in regional LN. Moreover, a high proliferation of CD8⁺ cells was observed when measuring absolute numbers of LN lymphocytes, thus producing an imbalance in the CD4/CD8 ratio at very early stages of the inflammatory process. These findings suggest a role for CD8⁺ and B lymphocytes in the latency period of AA at the LN level. Our results indicate a primary role for lymph nodes in initiating the inflammation of AA, whereas cells from the spleen probably play a secondary role.