Developmental status of CD4-CD8+ and CD4+CD8- thymocytes with medium expression of CD3

In normal mice, more than 10% of thymocytes in the CD4+CD8- and CD4-CD8+ single-positive (SP) subsets express a medium level of CD3 on the cell surface. However, the fate of CD3medium cells is unclear. The CD3medium SP subpopulations might contain (i) cells in an immature stage of the pathways leading to CD3high cells, (ii) cells in developmental pathways that do not lead to CD3high cells, or (iii) cells that have been negatively selected. We found that sorted CD3medium CD4+CD8- thymocytes from adult mice up-regulated CD3 to high levels in reaggregation thymus organ culture. Unlike their CD3high counterparts, CD3medium CD4+CD8- thymocytes were unable to undergo chemotaxis towards the chemokines CCL19 and CCL21. CD3medium thymocytes of both CD4+CD8- and CD4-CD8+ subsets were also considerably more responsive than CD3high SP cells to apoptotic signals induced in vitro by ligation of CD95 (Fas/APO-1) or by dexamethasone. In both SP subsets, a higher frequency of thymocytes expressing forbidden Vbeta+ T cell receptors reactive with endogenous mammary tumor virus superantigens was found in CD3medium subpopulations than in CD3high subpopulations. These findings argue that the CD3medium SP thymocyte subpopulations contain apoptosis-susceptible precursor cells of CD3high SP cells and are subject to negatively selecting pressures.     

Heterogeneity of the DN4 (CD44-CD25-) subset of CD4-CD8- double negative thymocytes; dependence on CD3 signaling

Recent studies have shown that apoptotic cell death associated with selection for thymocytes that express clonotypic TCRbeta or TCRgammadelta proteins takes place in the DN4 (CD44-CD25-) subset of CD4-CD8- double negative (DN) thymocytes. A detailed analysis of the DN4 subset is therefore of interest. Using intracellular (IC) staining for clonotypic TCR and CD3varepsilon proteins we find that DN4 cells consist of five subpopulations: TCRbetaIC(high)/CD3varepsilonIC(high)/TCRgammadeltaIC-, TCRbetaI-C-/CD3varepsilonIC(high)/TCRgammadeltaIC(+), TCRbetaIC(high)/CD3varepsilonIC(high)/TCRgammadeltaIC(+), TCRbetaIC(low)/CD3varepsilonIC(low)/TCRgammadeltaIC(-), and TCRbetaIC(-)/CD3varepsilonIC(-)/TCRgammadeltaIC(-). Expression levels of IC TCRbeta/CD3varepsilon, and of Thy1.2, CD2, and CD69 at the cell surface suggest that the TCRbetaIC(low)/CD3varepsilonIC(low)/TCRgammadeltaIC(-) subset harbors the direct precursors of DP cells, and is critical for life/death decisions in early thymic selection. TCRbeta/CD3varepsilon downregulation is less pronounced in DN4 and DP cells of mice deficient for CD3zeta or for p56(lck), suggesting that the dynamics of TCR protein regulation in the DN4 subset is dependent on CD3 signaling.     

Characterization of immature CD4+CD8-CD3- thymocytes.

Previously we have described (Hugo, P. et al., Int. Immunol. 1990. 2: 209) an immature CD4+CD8-CD3- thymocyte subset which is thought to be the counterpart of the CD4-CD8+CD3- subset. In this study we show that the ontogeny of these two subsets is parallel in fetal thymic organ culture. Extensive phenotypic characterization of CD4+CD8-CD3- cells reveals that they closely resemble CD4-CD8+CD3- thymocytes being: HSAhigh, Thy-1high, interleukin 2 receptor alpha chain negative, CD44-, H-2K+/-, CD5low, MEL-14low/intermediate, CD2+, LFA-1+ and MTS 35+. Finally, we show that the proportion of CD4+CD8-CD3- thymocytes is highly variable between mouse strains.     

Interferons alpha/beta inhibit IL-7-induced proliferation of CD4- CD8- CD3- CD44+ CD25+ thymocytes, but do not inhibit that of CD4- CD8- CD3- CD44- CD25- thymocytes.

Type 1 interferons (IFN-alpha/beta) have recently been shown to inhibit interleukin-7 (IL-7)-induced growth and survival of early B-lineage cells. The CD3- CD4- CD8- (triple negative; TN) thymocytes from normal mice strongly proliferated upon stimulation with IL-7 in suspension, culture. Such an IL-7-induced proliferation was suppressed by the addition of IFN-alpha/beta, but a fraction of the TN thymocytes still showed proliferation. The IL-7-induced growth of TN thymocytes from acid mice, which lack the CD44- CD25- subpopulation, was completely inhibited by the addition of IFN-alpha/beta. The IL-7 induced proliferation of CD4- CD8- thymocytes from T-cell receptor (TCR) transgenic mice, the majority of which are CD3+ CD44- CD25-, was resistant to IFN-alpha/beta-mediated suppression. In fetal thymus organ cultures (FTOC), the addition of IL-7 greatly increased the population of CD4- CD8- CD44+ CD25+ thymocytes and IFN-alpha/beta inhibited this IL-7-driven expansion. In contrast, the addition of IL-7 markedly decreased the percentages of CD4- CD8- CD3- CD44- CD25- cells, and IFN-alpha/beta reversed the effect and increased the subpopulations of CD44- CD25+ and CD44- CD25-. Finally, IFN-beta mRNA was found to be expressed in the thymus. The data suggest that type I interferons inhibit IL-7-driven proliferation of TN thymocytes, but do not block the normal differentiation process.     

Differentiation of CD4highCD8low coreceptor-skewed thymocytes into mature CD8 single-positive cells independent of MHC class I recognition

Thymocytes with a CD4^hiCD8^lo coreceptor-skewed (CRS) phenotype have been shown to contain precursors for CD8 single-positive (SP) thymocytes, in addition to precursors for CD4 SP cells. The selection mechanisms that stimulate CD4^hiCD8^lo cells to revert to the CD8 lineage are not known. Mice transgenic (tg) for the major histocompatibility complex (MHC) class I-restricted P14 T cell receptor (TCR), on the H-2^bm13 background, generate a large number of CD4^hiCD8^lo CRS thymocytes. We analyzed the developmental potential and the differentiation requirements of the CD4^hiCD8^lo population of these mice. Using reaggregate thymic organ cultures (RTOC), we observed that these cells efficiently and almost exclusively differentiate into CD8 SP cells. Differentiation occurred independent of whether or not the MHC haplotype of the thymic stroma corresponds to the MHC restriction of the tg TCR. Loss of CD4 was independent of thymic stroma, up-regulation of CD8 to full levels was dependent on thymic stroma but independent of MHC haplotype. After trypsin treatment and overnight incubation, these CRS cells re-expressed CD8 but failed to re-express CD4, indicating that they are in the process of terminating CD4 synthesis. CD8 SP cells derived from the CRS cells proliferate in response to peptide-pulsed antigen-presenting cells. Our data suggest that CD4^hiCD8^lo CRS thymocytes bearing the P14 tg TCR have completed positive selection and differentiate autonomously into functionally competent CD8 SP cells.     

Relationships between 2H4 (CD45RA) and UCHL1 (CD45RO) expression by normal blood CD4+CD8-, CD4-CD8+, CD4-CD8dim+, CD3+CD4-CD8- and CD3-CD4-CD8- lymphocytes.

We characterized and established relationships between the expression of membrane 2H4 (CD45RA) and UCHL1 (CD45RO) by enriched lymphocyte fractions prepared by selective immunomagnetic depletion of monoclonal antibody-defined populations. Cell fractions analysed in this study could be divided into two broad groups according to the presence (CD3+CD4+CD8-, CD3+CD4-CD8+, CD3+CD4-CD8dim+ and CD3+CD4-CD8-) or absence (CD3-CD4-CD8dim+ and CD3-CD4-CD8-) of the CD3 antigen. Preliminary studies confirmed a reciprocal relationship for CD45RA and CD45RO expression by major lymphoid components and further showed that the level or intensity of membrane 2H4 staining (2H4+, 2H4int and 2H4-) could be directly related to UCHL1 expression. As a reflection of their differential functions, the various CD3+ populations examined showed much greater heterogeneity in 2H4 and UCHL1 expression. CD3+CD4+CD8- cells generally showed significant proportions of 2H4+, 2H4int and 2H4- components, whereas the CD3+CD4-CD8+ population was characterized by a predominance of 2H4+ cells. The results of this current investigation further suggested a higher proportion of dual-positive (2H4+UCHL1+) cells and a much greater degree of inter-individual variation than previously suspected. In contrast to CD3+ lymphocytes, natural killer (NK) associated CD3-CD4-CD8dim+ and CD3-CD4-CD8- populations were mostly 2H4+ with only minor 2H4int components and very low expression of UCHL1. An additional observation of note was that the proportions of 2H4+ and 2H4- cells comprising the CD4+CD8- fraction in any given individual was highly correlated (P = 0.002) with the distributions of 2H4+ and 2H4- components within the CD4-CD8+ fraction. This suggests the possible existence of a common control mechanism for the acquisition of immunological memory by distinct lymphocyte populations and further indicates that individual variations in the distribution of 2H4/UCHL1 lymphocyte subpopulations may be a direct consequence of 'immunological experience' rather than age alone.     

'Radioresistant' CD4-CD8- intrathymic T cell precursors differentiate into mature CD4+CD8- and CD4-CD8+ T cells. Development of 'radioresistant' CD4-CD8- intrathymic T cell precursors

Using lectin (PNA) and monoclonal antibodies for Pgp-1, IL-2R, H-2k, CD3, and F23.1 (T cell receptor V beta 8), we characterized the 'radioresistant' CD4-CD8- double negative thymocytes at an early stage after 800 rad irradiation. Most of the CD4-CD8- cells on day 8 after irradiation expressed a high level of Thy-1, H-2k, and PNA, while a small proportion of these cells were CD3+ and/or F23.1+. The appearance of Pgp-1 and IL-2R on the 'radioresistant' double negative precursors was also sequentially examined from day 5 to day 9 after irradiation. The double negative thymocytes at day 5 expressed the highest level of Pgp-1 antigens and these cells gradually decreased in number from day 7 to day 9. By contrast, IL-2R was transiently expressed on the double negative cells on the day 7 and 8 after irradiation. These results indicate that progression of thymocyte development occurred within the CD4-CD8- thymocytes after irradiation. We further examined the homing ability of the double negative 'radioresistant' intrathymic T cell precursors to the periphery by intrathymic cell transplantation method. The double negative thymocytes proliferate and differentiate into CD4+CD8+ cells and CD4+CD8- cells but few CD4-CD8+ cells in the thymus, while only CD4-CD8+ cells were detected in the peripheral lymphoid organs 14 days after intrathymic transplantation of the double negative cells in the H-2 compatible Thy-1 congenic mice. These results suggest that the 'radioresistant' intrathymic precursors differentiate and mature in the thymus and migrate to the periphery.     

Analysis of clones derived from human CD7+CD4-CD8-CD3- thymocytes.

The differentiation of human thymocyte precursors was studied by analysis of clonal progeny of CD4-CD8-CD3- (triple negative or TN) thymocytes. Using a culture system of phytohemagglutinin, IL-2, and irradiated allogeneic lymphoid feeder cells, we found that 48% of clones (104 total) derived from TN thymocyte suspensions were TCR gamma delta cells, 12% of clones were TCR alpha beta cells, and 34% were CD16+CD3- cells. Importantly, 6% of clones were novel subsets of CD4+CD8-CD3- or CD4-CD8+CD3- thymocytes. The majority of TCR alpha beta, TCR gamma delta, and CD16+CD3- clones expressed low levels of CD4. Molecular analysis of freshly isolated TN- thymocytes prior to in vitro culture demonstrated that up to 40% of cells had TCR gamma, delta, and beta gene rearrangements, but were negative in indirect immunofluorescence assays for cytoplasmic TCR delta and beta. These data provide evidence at the clonal level for the presence of precursors of the TCR alpha beta and TCR gamma delta lineages in the human TN thymocyte pool. Moreover, a substantial proportion of freshly isolated human TN thymocytes had already undergone TCR gene rearrangement prior to in vitro culture. Whether these precursors of the TCR alpha beta and TCR gamma delta lineages mature from cells already containing TCR gene rearrangements into sTCR+ cells or differentiate in vitro from cells with TCR genes in germline configuration remains to be determined. Nonetheless, these data demonstrate that the predominant clone types that grow out of human TN thymocytes in vitro are TCR gamma delta and NK cells.     

小鼠CD3+TCRαβ+CD4-CD8-胸腺细胞特性分析

目的分析CD3+TCRαβ+ DN(double negative)胸腺细胞的特性,推断其在胸腺发育中表型和功能的成熟过程. 方法分离纯化小鼠胸腺DN细胞,用多重染色的方法分析CD3+TCRαβ+ DN细胞的表型和TCR库,并与外周淋巴结的相应细胞进行对比. 结果 DN胸腺细胞为异质性细胞,包括CD3- DN细胞和CD3+ DN细胞,而CD3+ DN细胞又分为CD3+TCRαβ+和CD3+TCRγδ+ 2个亚群.其中,CD3+TCRαβ+ DN细胞体积较小,绝大部分细胞对可的松耐受,细胞中能与自身反应的Vβ3+和Vβ11+细胞比例极低,表型较为成熟,与髓质型SP(single positive)细胞相当. 结论 CD3+TCRαβ+ DN细胞不同于CD3-TCRαβ- DN细胞,是一个独特的细胞亚群,只有在经历表型和功能的进一步成熟后才能迁出胸腺,移至外周.     

Presence of CD4 and CD8 determinants on CD4-CD8- murine thymocytes: passive acquisition of CD8 accessory molecules

In the present study we have examined the possibility that CD4 and CD8 accessory molecules can be passively acquired by thymocytes. We initially observed that most thymocytes contained within the CD4-CD8- subset actually possess low levels of CD4 and CD8 on their cell surface. However, the detection of CD4 and CD8 on CD4-CD8- cells was dependent on the presence of other CD4+/CD8+ thymocytes which were actively synthesizing CD4 and CD8. These initial findings suggested that the appearance of CD4/CD8 on "double-negative" thymocytes was due to the passive acquisition of these accessory molecules from CD4+/CD8+ cells present within the thymus. To investigate this possibility directly, we made both in vivo and in vitro mixes of thymocytes possessing different alleles of CD8 (Ly-2.1 and Ly-2.2). Under these experimental conditions, we detected Ly-2.2 on the surface of thymocytes that were genetically Ly-2.1+ and incapable of synthesizing Ly-2.2. These data indicate that thymocytes can express cell surface CD8 molecules which they have not produced but have acquired from other cells in their environment. Thus, the present study indicates that low-level surface expression of cell surface CD4/CD8 differentiation molecules does not necessarily identify distinct thymocyte subpopulations.     

Intrathymic selection of murine TCR alpha beta+CD4-CD8- thymocytes

The CD4-CD8- thymocyte population contains the precursors of all other thymocytes. However, it also contains a significant proportion of cells which express surface TCR alpha beta, and have little or no precursor activity. Like peripheral T cells, but unlike most other thymocytes, these TCR alpha beta+CD4-CD8- thymocytes do not express heat stable antigen. Both the origin and developmental status of these cells are unclear, and are the subject of this report. We have measured the proportion of V beta 8.1+ cells amongst TCR+HSA-CD4-CD8- thymocytes in MIs-1a versus MIs-1b mice, in order to determine whether they have undergone negative selection. The proportions were similar in both strains, in contrast to mature T cells, indicating that neither they nor their precursors had undergone clonal deletion. We also measured the accumulation of these cells over the early life of the animal and found that it was extremely slow. Our data also show that although TCR-V beta 8.1+ cells are reactive to MIs-1a in association with MHC class II, most mature TCR-V beta 8.1+ cells in MIs-1b mice are CD8+, suggesting an additional reactivity with MHC class I. We raise the possibility that TCR-V beta 8.1+CD4-CD8- thymocytes are derived from TCR-V beta 8.1+CD4+CD8+ thymocytes, and that the reactivity of TCR-V beta 8.1 with both MHC classes I and II has resulted in the down-regulation of both CD4 and CD8.     

CD4-CD8- thymocytes that express the T cell receptor may have previously expressed CD8

Amongst CD4-CD8- (double negative) thymocytes there is a sizeable population (variable from strain to strain) of cells expressing surface T cell receptor (TCR). These TCR+ double negatives are predominantly non-cycling, have very little precursor activity, and, unlike the TCR-CD4-CD8- thymocytes, appear not to be part of the mainstream of thymocyte development. A unique feature of this population is the biased V beta-gene region usage. In CBA mice, 60-70% of TCR+ CD4-CD8- cells express receptors that utilize V beta 8 gene products, compared with peripheral T cells from the same strain which are only 20-30% V beta 8+. This suggests that the high V beta 8 usage may be the result of some selective process. A growing body of experimental data suggests that TCR specificity selection occurs at the CD4+CD8+ stage of thymocyte development. In order to gain some insight into the previous history of the TCR+ double negatives, in particular whether or not they have previously expressed CD8 and therefore been eligible for selection, we have determined the methylation state of the CD8 gene and compared it to other thymocyte populations. We show that the TCR+ CD4-CD8- thymocytes are demethylated at some sites in the CD8 gene, consistent with previous CD8 expression. However, the demethylation pattern is distinct from that seen on typical peripheral T cells or on mature thymocytes, suggesting that the TCR+ CD4-CD8- thymocytes are not derived from mature thymocytes or peripheral T cells which have returned to the thymus and downregulated CD8 expression.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ontogeny of a novel CD4+CD8-CD3- thymocyte subpopulation: a comparison with CD4- CD8+ CD3- thymocytes

We have studied the ontogeny of a novel thymocyte subset, CD4+CD8-CD3-. Three-colour flow cytometric analysis demonstrated that these cells constituted approximately 1% of the total thymocyte content in adult CBA mice, and were not present in lymph nodes. They were mainly blastic, cortisone-sensitive, and localized in the outer thymic cortex. During foetal life they were first observed at day 15 and reached a maximum (6%) at day 17, beyond which they decreased to the adult level. This kinetic profile was similar to that of the CD4-CD8+CD3- subpopulation, except that the CD4+CD8-CD3- cells appeared slightly earlier and their percentage was lower. Both these populations appeared after the CD4-CD8-CD3- cells but before the CD4+CD8+CD3- cells. Similar observations were made during thymic reconstitution following dexamethasone treatment. In this case, both CD4+CD8-CD3- and CD4-CD8+CD3- thymocytes disappeared 48 h after the treatment. While their absolute number increased up to 14 days post-treatment, their percentage was maximal at day 7 post-treatment and returned to normal values by day 10 post-treatment. These results argue strongly that not only the CD4-CD8+CD3- population but also the CD4+CD8-CD3- population can be considered an intermediate precursor in CBA thymuses.     

Factor requirements for activation and proliferation steps of human CD2+CD3-CD4-CD8- early thymocytes

Human CD2+CD3-CD4-CD8- thymocytes were shown to display high in vitro growth ability although their factor requirements for activation and proliferation are not fully known. We have thus isolated these precursors and assayed their activation and proliferation potentials in response to various factors. Our results indicate that these cells proliferate in response to phytohemagglutinin (PHA), recombinant interleukin 2 (rIL 2) and rIL 4. Simultaneous addition of anti-CD2I + III monoclonal antibodies (mAb) and rIL 2 highly increased cell growth while IL 4-induced proliferation was not enhanced upon addition of anti-CD2. Anti-CD2 and PHA, but not IL 2, induced intracytoplasmic Ca2+ influx phosphatidyl inositol turnover as well as IL 2 receptor expression. Sequential studies indicated that CD2 triggering enable many more CD2+ precursors to respond to rIL 2. Endogenous IL 2 synthesis was necessary for PHA-induced cell growth. Neither of these in vitro treatment were able to induce membrane expression of CD3, CD4 or CD8 on CD2+ cells.     

CD4+CD25+调节性T细胞的发育与胸腺CD4-CD25+细胞关联性的探讨

目的:探讨CD4 CD25 调节性T细胞(CD4 CD25 regulatoryTcells,CD4 CD25 Tr)的发育及其与胸腺CD4-CD25 细胞的关系。方法:以流式细胞术检测小鼠从出生至发育成熟过程中,胸腺、脾脏、淋巴结和外周血中CD4 CD25 Tr比例变化,以及胸腺CD4-CD25 细胞比例变化;通过磁激活细胞分选(MACS)从小鼠淋巴结纯化CD4 CD25 T和CD4 CD25-T细胞,经CFDA-SE标记,以多种刺激形式诱导增殖。结果:小鼠出生1d到10周的发育过程中,胸腺CD4 CD25 Tr比例一直比较恒定,但在脾脏、淋巴结和外周血,随鼠龄增加而不断升高,从1d龄到1周时升高最迅速,其后的升高速度逐渐减慢,10周龄时达平台期。胸腺中CD4-CD25 细胞在出生1d的小鼠比例非常高,1d龄到1周龄期间迅速下降,10周龄时达平台期。ConA不能诱导CD4 CD25 Tr和CD4 CD25-T细胞增殖,但CD4 CD25 Tr出现一过性细胞增大;佛波醇酯加离子霉素能诱导CD4 CD25 Tr和CD4 CD25-T细胞增殖;包被的抗CD3抗体加可溶性抗CD28抗体能刺激CD4 CD25-T细胞增殖,但CD4 CD25 Tr不增殖,加入高浓度IL-2,CD4 CD25-T细胞增殖更强,CD4 CD25 Tr出现增殖。结论:胸腺CD4-CD25 细胞很有可能是CD4 CD25 Tr的前体。     

CD2‐mediated regulation of peripheral CD4+ CD25+ regulatory T‐cell apoptosis accompanied by down‐regulation of Bim

Extensive studies on CD4⁺ CD25⁺ regulatory T (Treg) cells suggest that they are important in regulating immune responses. However, mechanisms of peripheral Treg cell homeostasis are unknown. We found that stromal cells isolated from secondary lymphoid organs such as spleen and lymph nodes could support the survival of Treg cells. This was dependent on CD2 engagement and a direct interaction between Treg cells and stromal cells. In the presence of stromal cells, Bim, a pro‐apoptotic factor, was partially decreased in Treg cells. This effect could be inhibited by anti‐CD2 blocking antibodies, indicating that stimulation through CD2 on Treg cells regulates Bim expression, which may be relevant to Treg cell apoptosis. Therefore, Treg cell interactions with stromal cells through CD2 may be essential for Treg cell survival. Surprisingly, the expression of CD2 ligands on stromal cells was not detected. Hence, it is not clear how CD2 on Treg cells contributes to a direct interaction with the stromal cells and participates in survival support for Treg cells. Taken together, CD2 stimuli were mandatory for Treg cell survival with reduced Bim expression, but CD2 may not function as a direct receptor for molecules on stromal cells.     

Competition controls the rate of transition between the peripheral pools of CD4+CD25- and CD4+CD25+ T cells

Recent reports have hinted that it is possible to regenerate CD4+CD25+ regulatory T cells (Treg) from CD4+CD25- cells, a phenomenon termed conversion. We evaluated the relative contribution of this process to the Treg pool by transferring purified populations of CD4+ T cells into T cell-deficient mice. We report that conversion of CD25- cells into the CD4+CD25+Treg pool is minor if other bona fide CD25+ Tregs are present. Moreover, in the same hosts, the loss of CD25 expression by a population of Tregs also decreases in the presence of co-injected CD4+CD25- cells. Thus, the rate of exchange between CD25- and CD25+ T-cell populations is determined by the presence or absence of T-cell competitors. Our results attest for the role of competition in the contribution of different T-cell subsets for the regeneration of the peripheral CD4+ T-cell pool during lymphopenia.     

Development in vitro of human CD4+ thymocytes into functionally mature Th2 cells. Exogenous interleukin-12 is required for priming thymocytes to produce both Th1 cytokines and interleukin-10

Fresh postnatal thymocyte cell suspensions were directly cloned under limiting dilution conditions with either phytohemagglutinin or toxic shock syndrome toxin-1 (TSST-1), a bacterial superantigen. Cultures contained allogenic irradiated feeder cells and interleukin (IL)-2, in the absence or presence of exogenous IL-4, interferon (IFN)-γ or IL-12. The resulting CD4⁺ T cell clones generated under these different experimental conditions were then analyzed for their ability to produce IL-2, IL-4, IL-5, IL-10, IFN-γ and tumor necrosis factor (TNF)-β in response to stimulation with phorbol 12-myristate 13-acetate (PMA)+anti-CD3 monoclonal antibody or PMA + ionomycin. Different from T cell clones generated from peripheral blood, virtually all CD4⁺ T cell clones generated from human thymocytes produced high concentrations of IL-2, IL-4 and IL-5, but no IFN-γ, TNF-β or IL-10. Moreover, after activation, these clones expressed on their surface membrane both CD30 and CD40 ligand, but not the product of lymphocyte activation gene (LAG)-3, and provided strong helper activity for IgE synthesis by allogeneic B cells. The Th2 cytokine pattern could not be modified by the addition of IFN-γ. However, upon addition of exogenous IL-12, the resulting CD4⁺ thymocyte clones produced TNF-β, IFN-γ, and IL-10 in addition to IL-4 and IL-5. These results suggest that CD4⁺ human thymocytes have the potential to develop into cells producing the Th2 cytokines IL-4 and IL-5, whereas the ability to produce both Th1 cytokines and IL-10 is acquired only after priming with IL-12.     

CD3~-CD4~-CD8~ 小鼠胸腺细胞表型的研究

目的　分析CD3-CD4-CD8 胸腺细胞的表型特征 ,阐明其在胸腺发育中所处地位。方法　分离纯化小鼠CD4-CD8 单阳性胸腺细胞 ,进行CD3与其他表面标志的染色 ,然后进行FACS分析。结果　CD3-CD4-CD8 细胞体积较大 ,对可的松敏感 ,TCRαβ阴性 ,高度表达不成熟标志 6C10和HSA ,不表达活化标志CD6 9和成熟标志Qa 2。结论　CD4-CD8 单阳性胸腺细胞可明显分为CD3 和CD3-两个亚群 ,后者代表了胸腺发育过程中由CD4-CD8-双阴性细胞向CD4 CD8 双阳性细胞转变的过渡状态。