C D4＋ T细胞亚群在类风湿关节炎中的研究

类风湿关节炎（ rheumatoid arthritis, RA）是由多因素共同作用引起的自身免疫性疾病,至今发病机制仍未完全阐明, CD4＋T细胞在RA的发生发展中发挥重要作用。早期发现Th1／Th2细胞后,新的CD4＋T细胞亚群不断被发现,包括Th17细胞、 Treg细胞、 Th22细胞、 Th9细胞和Tfh细胞。不同CD4＋T细胞亚群在RA中表达异常,深入研究不同亚群CD4＋T细胞在RA中的作用可为RA的发病机制提供线索。     

Significance of Unconventional Peripheral CD4+CD8dim T Cell Subsets

Routine T cells phenotyping occasionally reveals a CD4+CD8dim T cell subset with an apparently homogeneous dot plot. The aim of this study was to elucidate their immunological significance from analysis of 31 healthy donors, 21 elderly and 220 immune deficient patients. CD4+CD8dim T cells expressed reduced levels of CD8 (11–17,000 compared to 96–128,000 mol/cell on CD8+ T Cells). CD4 was expressed at the same level as on CD4+ T cells. The occurrence of raised CD4+CD8dim T cells (> 20 cells/μL) was similar in kidney transplant recipients (28.4%) and healthy donors (26%). It was somewhat lower in HIV+ patients (19.7%) possibly due to virally induced CD4+ T lymphopenia. However, an age effect is possible because the occurrence was raised (33.3%) in 70 volunteers (chi2 test NS). On the other hand, the size of the CD4+CD8dim subset was not correlated with age. CD4+CD8dim T cells did not express the activation markers CD69 (n = 220) or CD25 (n = 10) and expressed the homodimeric (αα) isoform of CD8, suggesting they are related to mucosal immunity (MALT). We selected 29 patients with unambiguous dot plots. In 26 of them one predominant TCR Vβ clonotype was expressed on 18 to 94% of CD4+CD8dim T cells and never on more than 10% of conventional T cells. The predominant clonotypes were Vβ8 (n = 5), Vβ2 (n = 4), Vβ13.1 and Vβ 21 (n = 3 each). Whether this reveals a chronic stimulation or an emerging lymphoproliferative disorder must be elucidated. We propose to name this entity: “Oligoclonal Clonopathy of Undetermined Significance (OCUS).” An erratum to this article is available at.     

CD4+ T cell help improves CD8+ T cell memory by retained CD27 expression

CD4+ T cell help during the priming of CD8+ T lymphocytes imprints the capacity for optimal secondary expansion upon re-encounter with antigen. Helped memory CD8+ T cells rapidly expand in response to a secondary antigen exposure, even in the absence of T cell help and, are most efficient in protection against a re-infection. In contrast, helpless memory CTL can mediate effector function, but secondary expansion is reduced. How CD4+ T cells instruct CD8+ memory T cells during priming to undergo efficient secondary expansion has not been resolved in detail. Here, we show that memory CTL after infection with lymphocytic choriomeningitis virus are CD27(high) whereas memory CTL primed in the absence of CD4+ T cell have a reduced expression of CD27. Helpless memory CTL produced low amounts of IL-2 and did not efficiently expand after restimulation with peptide in vitro. Blocking experiments with monoclonal antibodies and the use of CD27(-/-) memory CTL revealed that CD27 ligation during restimulation increased autocrine IL-2 production and secondary expansion. Therefore, regulating CD27 expression on memory CTL is a novel mechanism how CD4+ T cells control CTL memory.     

Memory CD4 T cells: generation,reactivation and re‐assignment

Immunological memory is one of the features that define the adaptive immune response: by generating specific memory cells after infection or vaccination, the host provides itself with a set of cells and molecules that can prevent future infections and disease. Despite the obvious importance of memory cells, memory CD4 T cells are incompletely understood. Here we discuss recent progress in understanding which activated T cells surmount the barrier to enter into the memory pool and, once generated, what signals are important for memory cell survival. There is still, however, little understanding of how (or even whether) memory CD4 T cells are useful once they have been created; a surprising thought considering the critical role CD4 T cells play in all adaptive primary immune responses. In light of this, we will discuss how CD4 T memory T cells respond to reactivation in vivo and whether they are malleable to a re‐assignment of their effector response.     

Regulation of CD4 T Cell Reactivity to Self and Non-Self

While the thymus may be effective in inducing tolerance to lymphoid associated antigens, it is not as efficient in deleting T cells reactive to peripheral tissue specific antigens. Therefore, to maintain self tolerance to peripheral tissues, post-thymic mechanisms must be invoked. One important way to prevent autoimmune pathology mediated by autoreactive CD4 T cells is the diversion of clones to regulatory Th2 effector cells. However, many different factors contribute in vivo to the decision of stimulated CD4 T cells to develop into Th1 versus Th2 cells. For example, T cell signaling pathways may influence the types of cytokines produced by naive T cells, and studies have provided evidence for a genetic polymorphism among common mouse strains that can significantly influence the early cytokine production in stimulated naive CD4 T cells. The allele carried by the BALB/c strain promotes IL-4 production, and consequently provides resistance to autoimmune diabetes in our transgenic mouse model. In addition, antigen presenting cells can influence the development of stimulated CD4 T cells in part through the production of cytokines such as IL-12. The absorption of IL-12 in vivo can permit the expansion of Th2 type effector cells, and this phenomenon will also protect mice from autoimmunity. Finally, the relative potency of various class II positive antigen presenting cell types can influence the development of autoreactive T cells, with dendritic cells apparently being the strongest stimulator of Th1 responses. Consistent with this notion, a relB knockout mouse, which is missing dendritic cells, appears to drive Th2 development even in response to viral infection. In sum, these various influences over the Th1/Th2 decision in vivo may provide new targets for immunotherapy of autoimmune diseases.     

The phenotype and survival of antigen-stimulated transgenic CD4 T cells in vivo: the influence of persisting antigen

Naive and primed/memory CD4 T cells are distinguished by changes in the expression of activation/adhesion molecules that correspond with an altered function. Adoptively transferred TCR transgenic (tg) CD4 T cells specific for ovalbumin peptide (OVA-pep) were analysed for changing phenotype and the speed of change in vivo following antigen challenge with alum-precipitated (ap) OVA-pep, a conjugate that stimulated a Th2-type cytokine response. The change of CD45RB in relation to number of divisions showed that the transition from CD45RB(hi) (naive) to CD45RB(low) (primed/memory) was incremental; with each cell cycle the number of CD45RB(hi) molecules on the cell surface was diluted by approximately half and replaced by the low-weight isoform. Similarly, the change to CD44(hi) expression increased gradually during four rounds of proliferation. The loss of CD62L expression occurred early and was independent of cell division. CD69 was up-regulated quickly within 1-2 cycles, but down-regulated after about seven divisions. The expression of CD49d was not altered during the early rounds of division, although it was up-regulated on 30-60% of tg T cells dividing repeatedly (>or=8 cycles). When analysed on day 3 following stimulation, CD25 was no longer up-regulated. The intra-peritoneal injection of ap-OVA-pep stimulated tg T cells in the spleen and mesenteric lymph node one day in advance of those in more distant peripheral lymph nodes. Evidence indicated that residual antigen persisted for at least 4 weeks and was able to stimulate naive tg T cells. However, residual antigen had no net effect on extending or reducing survival of the transferred population.     

新生儿缺氧缺血性脑病患儿外周血CD4+CD25+调节性T细胞的变化及其意义

目的探讨CD4+CD25+调节性T细胞在新生儿缺氧缺血性脑病(HIE)患儿外周血的改变,及其在HIE疾病进程中的意义。方法用流式细胞术分析HIE组患儿92例和对照组31名外周血CD4+CD25+T细胞的变化,及其细胞内foxp3的表达变化。结果轻度、中度和重度HIE组患儿外周血CD4+CD25+T细胞比例分别为(9.26±1.18)%、(6.51±1.35)%和(5.36±1.54)%,对照组为(8.42±2.02)%。轻度HIE组患儿外周血CD4+CD25+T细胞较对照组有增高趋势,但差异无统计学意义(P>0.05);中度和重度HIE组患儿CD4+CD25+T细胞明显低于对照组,差异有统计学意义(P<0.05)。轻度、中度和重度HIE组患儿外周血CD4+CD25+foxp3+T细胞分别为(1.36±1.14)%、(1.21±0.94)%和(1.09±0.54)%,对照组为(1.30±1.17)%。轻度HIE组患儿CD4+CD25+foxp3+T细胞较对照组有增高趋势,但差异无统计学意义(P>0.05)。中度和重度HIE组患儿CD4+CD25+foxp3+T细胞明显低于对照组,差异有统计学意义(P<0.05)。结论中度和重度HIE组患儿CD4+CD25+foxp3+T细胞明显减少,这些调节性T细胞可能参与HIE的病理进程。     

CD38+ CD45RBlow CD4+ T cells: a population of T cells with immune regulatory activities in vitro

An antibody reactive with CD38 revealed both phenotypic and functional heterogeneity amongst CD45RB^low cells. Functional analysis of the CD38⁺ and CD38⁻ fractions showed that the latter contained T cells which responded to recall antigens and produced high levels of cytokine in response to polyclonal stimulation. In contrast, the CD38⁺ population failed to proliferate or to produce detectable levels of cytokines. Despite appearing unresponsive, the CD38⁺ population significantly inhibited anti-CD3-induced proliferation and cytokine secretion by the reciprocal CD38⁻ population. Immune suppression required stimulation through the TCR and was dependent on a physical interaction between regulatory and responding CD4⁺ populations. It did not involve killing of the responding T cells or secretion of IL-10 or TGF-β. Despite some similarities there is no direct correlation between the in vitro suppression characteristic of the CD38⁺ CD45RB^low subset and in vivo suppression which has been shown to be mediated by unseparated CD45RB^low CD4⁺ T cells. However, these results demonstrate that two functionally distinct subsets of T cells reside within the antigen-exposed or CD45RB^low CD4⁺ T cell population and are thus generated in vivo: (1) conventional memory T cells which proliferate and secrete cytokines in response to activation and (2) a population of regulatory T cells which inhibit T cell activation in vitro. Antibodies reactive with CD38 may provide a useful tool with which to study the role of these T cell subsets in the induction and regulation of the immune response.     

Differences in maintenance of CD8+ and CD4+ bacteria-specific effector-memory T cell populations

Our knowledge about the kinetics and dynamics of complex pathogen-specific CD8(+) T cell responses and the in vivo development of CD8(+) memory T cells has increased substantially over the past years; in comparison, relatively little is known about the CD4(+) T cell compartment. We monitored and directly compared the phenotypical changes of pathogen (Listeria monocytogenes)-specific CD8(+) and CD4(+) T cell responses under conditions leading to effective and long-lasting protective immunity. We found that the general kinetics of bacteria-specific CD8(+) and CD4(+) T cells during the effector and post-effector phases are synchronized. However, later during the memory phase, CD8(+) and CD4(+) T cell populations differ substantially. Whereas CD8(+) memory T cell populations with immediate effector function are readily detectable in lymphoid and non-lymphoid tissues and remain remarkably stable in size, antigen-specific CD4(+) effector-memory T cells decline continuously in frequency over time. These findings have important implications for the better understanding of the in vivo development of protective immunity towards intracellular pathogens.     

Mini-review CD4 T cells are required for CD8 T cell memory generation

Whereas the role of CD4 T cells in B cell memory generation is well established and unequivocal, the role that CD4 T cells play in CD8 responses was until recently far more elusive and controversial. A series of recent reports, however, have re-assessed the role of CD4 help on CD8 responses and have given rise to surprisingly unambiguous conclusions. While studying very different systems, they demonstrated that CD4 T cells are absolutely required for the generation of bona fide CD8 memory cells; the reports allow, for the first time, strong analogies to be made between B and CD8 memory cell generation. These data invite us to drastically change our idea of CD4 help on CD8 responses because they show that the old dichotomy - Th-dependent versus Th-independent CD8 responses - is no longer accurate.     

Age-related increase in the fraction of CD27-CD4+ T cells and IL-4 production as a feature of CD4+ T cell differentiation in vivo.

The influence of ageing on phenotype and function of CD4+ T cells was studied by comparing young (19-28 years of age) and aged (75-84 years of age) donors that were selected using the SENIEUR protocol to exclude underlying disease. An age-related increase was observed in the relative number of memory cells, not only on the basis of a decreased CD45RA and increased CD45RO expression, but also on the basis of a decrease in the fraction of CD27+CD4+ T cells. Our observation that the absolute number of CD45RO+CD4+ T cells was increased, while absolute numbers of CD27-CD4+ T cells remained unchanged in aged donors, indicates that the latter subset does not merely reflect the size of the CD45RO+CD4+ T cell pool. The increased fraction of memory cells in the aged was functionally reflected in an increased IL-4 production and T cell proliferation, when cells were activated with the combination of anti-CD2 and anti-CD28, whereas IL-2 production was comparable between both groups. No differences were observed with respect to proliferative T cell responses or IL-2 production using plate-bound anti-CD3 or phytohaemagglutinin (PHA). The observation that IL-4 production correlated with the fraction of memory cells in young donors but not in aged donors suggests different functional characteristics of this subset in aged donors.     

Membrane CD45R isoform exchange on CD4 T cells is rapid,frequent and dynamic in vivo

CD4 T cells bearing high (240–190 kDa) and low (180 kDa) molecular mass isoforms of the leukocyte common antigen CD45 define functionally distinct subsets which have been equated with naive and memory T cells. In the rat, CD4 T cells expressing a high molecular mass isoform [identified by monoclonal antibody MRC-OX22 (anti-CD45RC)] exchange this for the 180 kDa molecule (CD45RC^?) when stimulated by antigen. Here we show, by transferring mature allotype-marked CD45RC^? CD4 T cells (depleted of immature Thy-1⁺ CD45RC^? recent thymic emigrants) into normal euthymic recipients, that many T cells re-express the high molecular mass isoform in less than 6 h. By 24 h, 30–60% of CD45RC^? CD4 T cells became CD45RC⁺; within a week the entire cohort appeared to exchange the low for the high molecular mass isoform. Isoform exchange was dynamic and many CD4 T cells returned once again to the CD45RC^? state. CD45RC^? CD4 T cells declined in number more rapidly than the CD45RC⁺ subset after transfer. The results suggest that CD45R isoforms distinguish between resting T cells (CD45RC⁺) and those which have encountered antigen in the recent past. CD45R isoforms would appear to be unsuitable markers of naive and memory T cells.     

Regulation of CD4 T cells and their effects on immunopathological inflammation following viral infection

CD4 T cells help immune responses, but knowledge of how memory CD4 T cells are regulated and how they regulate adaptive immune responses and induce immunopathology is limited. Using adoptive transfer of virus‐specific CD4 T cells, we show that naive CD4 T cells undergo substantial expansion following infection, but can induce lethal T helper type 1‐driven inflammation. In contrast, memory CD4 T cells exhibit a biased proliferation of T follicular helper cell subsets and were able to improve adaptive immune responses in the context of minimal tissue damage. Our analyses revealed that type I interferon regulates the expansion of primary CD4 T cells, but does not seem to play a critical role in regulating the expansion of secondary CD4 T cells. Strikingly, blockade of type I interferon abrogated lethal inflammation by primary CD4 T cells following viral infection, despite that this treatment increased the numbers of primary CD4 T‐cell responses. Altogether, these data demonstrate important aspects of how primary and secondary CD4 T cells are regulated in vivo, and how they contribute to immune protection and immunopathology. These findings are important for rational vaccine design and for improving adoptive T‐cell therapies against persistent antigens.     

Induction and function of virus-specific CD4+ T cell responses

CD4+ T cells - often referred to as T-helper cells - play a central role in immune defense and pathogenesis. Virus infections and vaccines stimulate and expand populations of antigen-specific CD4+ T cells in mice and in man. These virus-specific CD4+ T cells are extremely important in antiviral protection: deficiencies in CD4+ T cells are associated with virus reactivation, generalized susceptibility to opportunistic infections, and poor vaccine efficacy. As described below, CD4+ T cells influence effector and memory CD8+ T cell responses, humoral immunity, and the antimicrobial activity of macrophages and are involved in recruiting cells to sites of infection. This review summarizes a few key points about the dynamics of the CD4+ T cell response to virus infection, the positive role of pro-inflammatory cytokines in the differentiation of virus-specific CD4+ T cells, and new areas of investigation to improve vaccines against virus infection.     

CD4+CD25+调节性T细胞在自身免疫病中作用的研究进展

CD4 CD25 调节性T细胞具有独特的免疫抑制功能,通过细胞接触和细胞因子机制抑制自身反应性T细胞的活化与增殖,在自身免疫病中发挥着重要作用。通过研究CD4 CD25 调节性T细胞在自身免疫病中的作用,将会揭示这类疾病的发病机制,从而为治疗自身免疫病提供一个新途径。     

Peripheral T lymphocyte depletion by apoptosis after CD4 ligation in vivo: selective loss of CD44- and 'activating' memory T cells.

We have demonstrated that a single intravenous bolus of rat anti-CD4 MoAb caused a small but prolonged increase in apoptosis in murine lymph nodes. We have quantified this process using the novel Highly Optimized Microscope Environment (HOME) interactive images analysis system and shown that the increase in apoptosis was sufficient to account for the observed depletion of the peripheral CD4+ T cell subset. This occurred in the absence of any other exogenous signal. Furthermore, there was no evidence of an inflammatory or necrotic response in the tissues, indicating that this was unlikely to be Fc or complement-mediated antibody killing. The anti-CD4-induced depletion selectively removed CD44- T cells. Using mice previously immunized with yeast-derived HIV-1 p24 recombinant protein there was sparing of memory T cell function after in vivo anti-CD4 treatment, except during a window of less than 24 h duration, when simultaneous exposure to antigen and anti-CD4 antibody resulted in the depletion of specific memory T lymphocyte function. This indicated that a very minor alteration in the frequency of apoptosis had a marked effect on cell number over time, and suggested that opportunistic infection associated with CD4+ T cell depletion may be explained by loss of memory cells when there is antigenic stimulation at the same time as CD4 ligation. These results have implications for the pathology of HIV-associated disease which is associated with ligation of CD4 molecules in vivo.     

Distinct roles for CD4 and CD8 as co-receptors in T cell receptor signalling

We demonstrate that CD4 and CD8 modify signals induced through the T cell receptor for antigen (TCRαβ) in distinct fashions. Pretreatment of CD4⁺ lymph node T cells with CD4-specific monoclonal antibody results in a tenfold inhibition of DNA synthesis induced by anti-TCRαβ. In contrast, pretreatment of CD8⁺ T cells with CD8-specific mAb has no effect on DNA synthesis subsequently induced through TCRαβ. While inhibiting late activation signals, pretreatment with anti-CD4 does not detectably alter the pattern of anti-TCRαβ-induced tyrosine phosphorylation of cellular proteins, nor subsequent Ca²⁺ mobilization. The distinct biological consequences of anti-CD4 and anti-CD8 pretreatment correlate with the differential association of their respective ligands with the cellular protein tyrosine kinase, p56^lck. While both T cell lineages contain similar levels of cellular p56^lck, tenfold more is associated with CD4 than with CD8. This difference is associated with the differential effects of pretreatment with anti-CD4 and anti-CD8 on the distribution and activity of p56^lck. Further, antibody-mediated aggregation of TCRαβ on CD4⁺ T cells induces the appearance of a p56^lck species with decreased mobility in sodium dodecylsulfate-polyacrylamide gel electrophoresis. This effect is observed in CD4⁺ T cells exclusively and involves the fraction of p56^lck which is not associated with CD4. The results presented here demonstrate that the signalling elements which couple the antigen receptor to second messenger-generating systems are under distinct physical and/or functional constraints in the two T cell lineages.     

CD3-induced apoptosis of CD4+CD8+ thymocytes in the absence of clonotypic T cell antigen receptor

Clonal selection of T cells mediated through the T cell antigen receptor (TCR) mostly occurs at the CD4⁺CD8⁺ double positive thymocyte stage. Immature CD4⁺CD8⁺ thymocytes expressing self-reactive TCR are induced to die upon clonotypic engagement of TCR by self antigens. CD3 engagement by antibody of the surface TCR-CD3 complex is known to induce apoptosis of CD4⁺CD8⁺ thymocytes, a process that is generally thought to represent antigen-induced negative selection in the thymus. The present study shows that the CD3-induced apoptosis of CD4⁺CD8⁺ thymocytes can occur even in TCRα^? mutant mice which do not express the TCRαβ/CD3 antigen receptor. Anti-CD3 antibody induces death of CD4⁺CD8⁺ thymocytes in TCRα^? mice either in cell cultures or upon administration in vivo. Interestingly, most surface CD3 chains expressed on CD4⁺CD8⁺ thymocytes from TCRα^? mice are not associated with clonotypic TCR chains, including TCRβ. Thus, apoptosis of CD4⁺CD8⁺ thymocytes appear to be induced through the CD3 complex even in the absence of clonotypic antigen receptor chains. These results shed light on previously unknown functions of the clonotype-independent CD3 complex expressed on CD4⁺CD8⁺ thymocytes, and suggest its function as an apoptotic receptor inducing elimination of developing thymocytes.