Characterization of T lymphocyte subsets with monoclonal antibodies: discovery of a distinct marker, Ly-m22, of T suppressor cells

The study of cell surface antigens has accelerated in the few years since the advent of hybridoma technology to the point where many dozens of such markers have now been described. The functional heterogeneity of post-thymic T cells in the immune response, however, still exhibit complexities beyond the resolving power of our current repertoire of marker antigens. In this study, we investigated the surface phenotype of three types of effector T cells: helper cells, nonspecific suppressor cells, and cytotoxic T cells, using four recently discovered alloantigen systems of T cells: Ly-m10, Ly-m18, Ly-m19, and Ly-m22. SRBC-primed spleen cells were used as a source of specific helper T cells, and they were tested by their ability to promote antibody synthesis by B lymphocytes. Concanavalin A-activated suppressor cells were assayed by their ability to inhibit that response. Cytotoxic T cells were activated by alloantigen. We found Ly-m10 to be expressed on all three cell types tested, whereas Ly-m18 and Ly-m19 were absent from all three. Ly-m22, whose controlling locus is closely linked to the Mls region, had a unique distribution, being present solely on suppressor cells. Thus Ly-m22 emerged as a new marker that distinguishes nonspecific T suppressor cells (Ly-m22+) from T helper as well as cytotoxic T cells (Ly-m22-). Ly-m22 is the only antigen besides I-J so far known to be restricted to suppressor cells.     

Markers of cell lineage, differentiation and activation

The most widespread use of CD markers is in the determination of cell lineage and sublineage. For example, T cells are identified by the expression of CD3 (reviewed in this issue of CD corner). A mature T cell may belong to the T4 subset, in which case it will express CD4. Similarly, there are markers for other cell populations and sub-populations. Within the lineages, it is helpful to distinguish cells at different stages of differentiation and activation. Differentiation status is particularly useful in the diagnostic analysis of the lymphoid and myeloid malignancies, and in research on the haemopoietic system. Examples include markers for na?ve or antigen-experienced cells (especially the CD45 isoforms) and molecules such as CALLA (CD9) found on B-lineage precursors, including B lineage acute lymphoblastic leukaemia. Activation status is especially interesting in studies of cell function. Activation markers include growth factor receptors such as CD25 (a component of the receptor for IL-2), and molecules who's cellular function is not fully understood, such as CD69 and CD98. These markers have revolutionised aspects of pathology and research, and the ease with which some cell populations can be identified has lead to some unrealised, and perhaps unrealistic, expectations. We expect to be able to identify T helper type 1 (TH1) and T helper type 2 (TH2) cells on the basis of a simple surface marker; we are frustrated by the lack of a single marker for all dendritic cells or for all NK cells; we are confused by the un-coordinated expression of different activation markers; we tend to over-interpret phenotype in some situations. To find solutions to these problems it is helpful to examine why the successful lineage markers work so well, and to reconsider our expectations. Lineage markers are the main focus in this commentary; the question of activation markers and markers of differentiation state will be considered in a separate paper.     

A human CD4- T cell leukemia subclone with contact-dependent helper function.

Helper T lymphocytes provide a contact dependent signal to resting B cells that is required for optimal differentiation into Ig-secreting cells. The surface structure(s) on T cells that mediate helper function have not been identified but are known to be induced by T cell activation. A CD4- subclone of the Jurkat leukemic T cell line (D1.1) was isolated and found to be distinct from CD4+ Jurkat clones and a variety of other T and non-T cell leukemic lines in that coculture of D1.1 with resting B cells induced B cells to specifically express surface CD23 molecules, a marker of B cell activation. Furthermore, Jurkat D1.1 induced B cell proliferation and terminal B cell differentiation into IgG-secreting cells in the presence of T cell-dependent B cell mitogens. Similar to the helper effector function of activated T cells, the effects of Jurkat D1.1 were neither Ag nor MHC restricted. Paraformaldehyde fixed Jurkat D1.1 cells remained competent to activate B cells while D1.1 supernatants and diffusible factors were inactive. The effect of Jurkat D1.1 on B cell activation was distinct from that of rIL-4 and was not inhibited by antibodies to IL-4. Together these observations suggested that surface structures on D1.1 and not secreted factors, mediated contact-dependent helper effector function.     

In vitro locomotion of allosensitized T lymphocyte clones in response to metabolites of arachidonic acid is subset specific

The effects of the arachidonic acid metabolites prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) on the in vitro random migration of cloned murine T lymphocytes (derived from limiting dilution analysis of a C57BL/6 anti-DBA/2 mixed leukocyte culture) were examined. Experiments were also performed to study the effects of the cyclooxygenase inhibitor indomethacin on both random lymphocyte migration and lymphocyte migration in the presence of PGE2. The responses of cloned lymphocytes to PGE2 and LTB4 were compared with those of unsensitized lymph node lymphocytes. PGE2 at 100 ng/ml significantly inhibited (p less than 0.001) the in vitro migration of helper clones of T lymphocytes, but had no effect on random migration of cytotoxic T cells or helper independent cytotoxic (HIT) cloned cells. In contrast, LTB4 significantly (p less than 0.001) enhanced the random locomotion of helper, cytotoxic, and "HIT" cloned cells at 0.1 and 0.3 ng/ml. The effects of both PGE2 and LTB4 were found to be completely reversible by cell washing. Indomethacin (10(-7) M) did not alter random migration of any of the clones, and in particular, did not affect the inhibition of helper lymphocyte migration induced by PGE2. Unsensitized bulk lymph node lymphocyte migration was not affected by either PGE2 or LTB4. The results suggest that modulation of lymphocyte locomotor function by environmental stimuli may depend on cellular activation, and the locomotor responses of activated lymphocytes to arachidonic acid metabolites may be subset specific.     

Role of Ly-1:Qa1- and Ly-1:Qa1+ inducer T cells in activation of Ly-23 effectors of suppression of antibody production in mice

Ly-2+ effectors of T cell-mediated suppression require inducing signals from antigen and a helper cell bearing the Ly-1+:Qa1+ surface phenotype. In this report, we have further examined the helper cell requirements for suppressor cell induction of antibody production in mice. By using the T cell subset education procedure in vitro, we have activated T cells to sheep red blood cells (SRBC) antigens and then purified Ly-2 cells before testing for suppressor activity in assay cultures of defined T and B cell subsets. We have confirmed our previous observations that Ly-1+:Qa1+ cells are required for activation of T suppressors, but have found that under the appropriate conditions, there is not a strict requirement for the Ly-123 subset of T cells. Furthermore, if Ly-23 cells are stimulated in the presence of Ly-1+:Qa1- T cells, effective suppressors can be obtained only if a source of Ly-1:Qa1+ inducers is added to the assay culture. If Ly-23 cells are activated by antigen in the absence of Ly-1 cells, subsequent exposure to the Ly-1+:Qa1+ subset under the conditions tested here is not sufficient to activate suppressors. These results show that effectors of suppression, like B cells and cytotoxic T lymphocytes, may respond to two helper cells.     

CD31, a novel cell surface marker for CD4 cells of suppressor lineage, unaltered by state of activation.

In this study, we examined the role of CD31 as a cell surface marker for subsets of human CD4 cells. CD31, as defined by a newly developed mAb termed anti-1F11, can divide activated as well as resting CD4 cells into distinct functional subpopulations, based on its surface expression. Among CD4 cells freshly isolated from peripheral blood, anti-1F11 preferentially reacts with the CD45RA+ subset. The majority of helper activity for B cell IgG synthesis and memory function to recall Ag such as tetanus toxoid or mumps was found within the CD31- CD4 cell population, whereas CD31+ CD4 cells provided poor helper function for B cell IgG synthesis and were more responsive to Con A and autologous MHC (autologous MLR). The expression of CD31 on CD45RA+ CD4 cells did not change after activation, despite the loss of CD45RA from the cell surface. Conversely, CD31 was not acquired after activation of CD45RO+ CD45RA- CD4 cells. Furthermore, activated CD4 cells expressing CD31 can induce suppressor function for B cell IgG synthesis, whereas the reciprocal population of activated CD4 cells (CD31-) provide strong helper function for B cell IgG production. Finally, IL-4 production could only be induced by stimulation with PMA and ionomycin in either resting or activated CD31- CD4 cells. Thus, CD31 may prove useful in defining CD4 populations with reciprocal functional programs. Moreover, unlike other markers used for this purpose, the expression of CD31 does not change after activation and may serve as a more useful marker for identification of cells of suppressor or helper lineage.     

Nonopiate active proenkephalin-derived peptides are secreted by T helper cells

Recent investigations have shown that the neuroendocrine and immune systems profoundly affect each other. In part, these interactions occur via common chemical messengers and receptors. One possible shared chemical messenger is the opioid precursor preproenkephalin, for which high concentrations of messenger RNA are present in brain, adrenal, and activated T helper cells. Because the biologic action of most peptide messengers depends on the posttranslational processing of the precursor, we have examined T helper cell lines for the production of proenkephalin-derived peptides. These peptides were characterized by multiple radioimmunoassays, gel filtration chromatography, and opiate radioreceptor assays. We found that activated T helper cells secrete significant concentrations of high-molecular-weight, opiate-inactive peptides, which are distinct from the proenkephalin-derived peptides of the neuroendocrine system. These studies clearly indicate cell-specific processing of proenkephalin, and suggest that the T helper cell-secreted products may have nonopiate receptor-mediated actions.     

Identification of a previously unknown antigen-specific regulatory T cell and its mechanism of suppression

Despite increasing evidence for the existence of antigen-specific regulatory T cells, the mechanisms underlying suppression remain unclear. In this study we have identified and cloned a novel subset of antigen-specific regulatory T cells and demonstrated that these T cells possess a unique combination of cell surface markers and array of cytokines. The regulatory T cells are able to inhibit the function of T cells carrying the same T-cell receptor specificity and prevent skin allograft rejection in an antigen-specific, dose-dependent manner. The regulatory T cells are able to acquire alloantigen from antigen-presenting cells, present the alloantigen to activated syngeneic CD8+ T cells and then send death signals to CD8+ T cells. These findings provide a novel mechanism of regulatory T-cell-mediated, antigen-specific suppression.     

辅助噬菌体在噬菌体展示中的应用及研究进展

噬菌体展示技术是一种将外源肽或蛋白质与特定噬菌体衣壳蛋白相融合,展示于噬菌体表面来构建蛋白质或多肽文库,并从中筛选目的蛋白、多肽或抗体的基因工程高新技术。噬菌粒/辅助噬菌体系统是最常用的噬菌体展示系统,此系统中辅助噬菌体对噬菌粒的复制和组装发挥着至关重要的作用。本文结合当今该领域的最新研究动态,概述了噬菌粒和辅助噬菌体双基因组系统,着重介绍了不同辅助噬菌体的特点及其突变机制,并对其应用前景进行了展望,以期为该技术的进一步完善提供一定的借鉴作用。     

Stages of T cell activation: continued antigen dependence of IL 2-producing cells after IL 2 receptor expression

Alloantigen stimulation leads, within 48 to 72 hr, to the expression of IL 2 receptors (IL 2R) on the surface of most of the helper T cells with specificity for the stimulating antigens. The IL 2R-bearing cells, separated by flow cytometry from 3-day human or mouse mixed lymphocyte cultures, were found by limiting dilution methods to be enriched 10- to 20-fold (compared to IL 2R- cells) for antigen-specific helper T cells detected by IL 2 production. Although these cells have been activated to an IL 2R+ stage, most of them are unable to produce detectable IL 2 unless they are cultured together with the original, activating antigen. Even when IL 2 is supplied, and lymphokine production measured by assay of a second factor, IL 3, the large majority of individual activated helper T cells remain dependent on further antigenic exposure for their continued maturation into lymphokine-secreting effectors. Helper T cells at this early stage of activation can therefore proliferate when given IL 2 alone, but lymphokine secretion involves a second antigen-dependent step.     

Regulation of mucosal IgA production in vitro by autoreactive immunoregulatory T cells from murine Peyer's patches

In this study, we investigated whether Peyer's patch-derived T-cell subsets participate in vitro in self major histocompatibility (MHC) class II antigen (Ag)-mediated immunoregulatory circuits for gut-mucosal IgA isotype selection in the presence of Peyer's patch (PP)-derived syngeneic surface immunoglobulin M (sIgM)-bearing B cells. When fresh (in vitro unstimulated) sIgM-bearing B cells were cocultured with fresh, PP-derived L3T4+ Vicia villosa-nonadherent (VV-) T cells (T helper (Th) cells), the production of all class-specific immunoglobulins (Ig), but, in particular, IgA, was enhanced two- to sixfold. This augmented Ig production was, however, reduced by nearly 50% when fresh PP-derived Lyt2+ VV-T cells (suppressor T cells) were added. Furthermore, addition of PP-derived L3T4+ VV+ and Lyt 2+ VV+ T cells abrogated, by nearly 100%, the suppression induced by the Lyt 2+ VV-T cells (contrasuppression). When lipopolysaccharide (LPS)-stimulated, PP-derived sIgM-bearing B cells were cocultured with the Th cells, the production of each class-specific Ig was similarly enhanced, but Ig levels exceeded those obtained with cultures of the unstimulated B cells (P less than 0.001). Anti-I-A or anti-I-E monoclonal antibody (mAb) inhibited the induction of each immunoregulatory T-cell effector activity (P less than 0.001), and anti-I-A/E inhibited it synergistically. Thus, unstimulated fresh PP-derived T cells appear to be activated and then to exert T-cell effector functions in the sequential development of helper, suppressor, and contrasuppressor immunoregulatory networks in the presence of PP-derived sIgM B cells and, particularly, LPS-preactivated sIgM B cells. Based on the blocking effect of anti-I-A and/or anti-I-E mAb on the induction of each T-cell-mediated immunoregulatory function in class-specific Ig production, it appears that the autoreactive (self MHC class II Ag-reactive) activation of PP T cells evoked by Ia Ag on PP sIgM B cells largely controls mucosal IgA production by the latter cells. Furthermore, this immunoregulation by autoreactive effector T cells, especially the L3T4+ VV- helper T cell, may play a significant role in vivo in gut-mucosal IgA isotype production.     

Helper B cells promote cytotoxic T cell survival and proliferation independently of antigen presentation through CD27/CD70 interactions

CD8-expressing cytotoxic T cell (CTL) interactions with APCs and helper T cells determine their function and ability to survive. In this study, we describe a novel interaction independent of Ag presentation between activated CTLs and bystander CD19-expressing B lymphocytes. Ag-stimulated CTLs serially engage autologous B lymphocytes through CD27/CD70 contact that promotes their survival and proliferation. Moreover, these interactions induce the release of proinflammatory cytokines that follows two general patterns: 1) an epitope-dependent enhancement of cytokine release, and 2) a previously undiscovered coordinate release of cytokines independent of epitope exposure. The latter includes chemoattractants targeting activated T cells. As a result, activated T cells are attracted to B cells, which exert a "helper" role in lymphatic organs or in areas of inflammation. This observation provides a mechanistic explanation to previously reported experimental observations suggesting that B cells are required for T cell priming in vivo.     

MHC-linked immune response suppression mediated by T cells bearing I-A-encoded determinants

The immune response to chicken egg-white lysozyme (HEL) is actively and specifically regulated by antigen-specific T cell-mediated suppression in mice bearing the H-2b haplotype; the suppression is therefore MHC-linked. In this report, we propose a possible mechanism for MHC-linked suppression of HEL-helper T cells based on expression of I region-encoded cell surface determinants. We determined whether inhibition of anti-HEL antibody responses correlated with expression of serologically detectable I-A-encoded cell surface determinants by antigen-specific helper, suppressor-inducer, or suppressor-effector T cells. It was observed that HEL-suppressor-effector T cells, but not helper or suppressor-inducer T cells, were eliminated after treatment with anti-I-Ab antibody and complement. Furthermore, suppressor-effector T cells co-express Thy-1, Lyt-2, and I-A cell surface antigens. These results raise the possibility that HEL-specific helper T cells become functionally inhibited after recognition of HEL and I-A alloantigen displayed by suppressor-effector T cells. Thus, the interaction between helper and suppressor T cells may be analogous to the mechanism of T cell-B cell interaction.     

Serologic and immunochemical characterization of HLA-A9 xenoantisera

There was a pronounced quantitative difference between the helper activities of B6C3F1 splenic T cells sensitized with unmodified vs modified antigens of SRBC. Modified SRBC induced the greater helper activity which was measured by the magnitude of an anti-TNP response (IgM and IgG) elicited in vivo by virgin B lymphocytes. Antigen modification was produced by conjugating SRBC with the hapten or simply by incubating SRBC in cacodylate buffer. There were restrictions with respect to both erythrocyte species and mouse strains for this differential priming to occur. The relatively poor performance of SRBC-primed T lymphocytes was apparently not due to suppressor T cells, but rather to activation of only one of two identified T cell subpopulations required for full helper activity. Unmodified SRBC activated a subpopulation of "helper" cells characterized as sensitive to elimination by ATS and long-lived after ATx, but failed to activate in B6C3F1 mice a second subpopulation of "amplifier" cells resistant to elimination by ATS and short-lived after ATx. In contrast, modified SRBC activated both helper and amplifier cells. Under appropriate conditions these subsets of T cells were strongly synergistic in promoting antihapten antibody formation especially of the IgG class. The involvement of two distinct types of T lymphocytes in the positive regulation of antibody responses raises interesting and novel questions concerning the sequence of events in the triggering of B cells and the subsequent development of the response.     

Both naive and memory T cells can provide help for human IgE production, but with different cytokine requirements.

Most in vitro systems for the induction of IgE production by human B cells require both IL-4 and the presence of T cells. Little is known about the mechanism of T cell help or the ability of different T cell subsets to provide this helper activity. In the present study we demonstrate that, in the presence of exogenous IL-4, anti-CD3 stimulated naive T cells (CD4+CD45RA+) are potent helper cells for human IgE production. In their presence, as little as 750 autologous B cells can produce up to 100 ng/ml IgE. This response was found over a broad range of anti-CD3 concentrations. IgE helper activity by naive T cells was inhibited by IL-2. Under all conditions tested, naive T cells were unable to provide help for IgM production. This is in contrast to activated memory T cells (CD4+CD45RO+), which are very efficient helper cells for IgM or IgE production, provided that IL-2 or IL-2 plus IL-4 are present respectively.     

Activation requirements of cloned inducer T cells. II. The failure of some clones to respond to antigen presented by activated B cells

Inducer/helper T cells recognize nominal antigen in association with Ia on the surface of the antigen-presenting cell (APC). Recent studies have shown that B cells can effectively function as APC. In the present study we have assessed the ability of cloned inducer T cells to discriminate between activated B cells or splenic macrophages as APC. We found that most of the clones tested demonstrated an equivalent response to antigen presented by activated B cells or splenic adherent cells. Some clones were very efficiently stimulated by antigen presented by activated B cells, whereas other clones failed to respond or responded very poorly when activated B cells were used to present antigen. We attempted to determine the mechanism responsible for the inability of certain clones to proliferate in response to antigen presented by activated B cells.     

Functional analysis of human T cell subsets defined by monoclonal antibodies. V. Suppressor cells within the activated OKT4+ population belong to a distinct subset

In the present report, we characterize a monoclonal antibody directed at a surface differentiation antigen on human T cells. The monoclonal antibody, OKT17, recognizes a cell surface antigen present on the majority of resting normal peripheral T cells. In contrast, OKT17 is unreactive with normal B cells, B cell lines, T cell lines, or SIg+ CLL. Interestingly, after activation, the antigen recognized by OKT17 is lost from a subset of OKT4+ cells. We took advantage of this finding to explore further the functional heterogeneity within activated OKT4+ cells. Evidence was obtained that the PWM-activated OKT4+ subset remaining after depletion of OKT17-reactive T cells (OKT4+ 17-) contains radiosensitive helperr cells but is devoid of suppressor cells. In contrast, the activated OKT4+ 17+ population contains potent radiosensitive suppressor cells as well as radioresistant helpe cells. Taken together, these studies suggest that the OKT17 monoclonal antibody can differentiate two functionally mature, activated OKT4+ human T cells: OKT4+ OKT17+ radiosensitive suppressor cells and OKT4+ 17- radiosensitive helper cells.     

Th17细胞及其在器官移植排斥反应中的作用

最近发现的辅助T细胞17（T helper cell 17,Th-17）是不同于辅助T细胞1型（Thelpercell1,Th-1）,辅助T细胞2型（Thelpercell2,Th-2）及调节性T细胞（regulatory T cell,Treg）的T细胞亚群,有其独立的分化和发育调节,且互相影响。它由初始T细胞在转化生长因子B（transforming growth factor B,TGF—B）与白细胞介素6（interleukin6,IL-6）、白细胞介素23（interleukin23,1L23）联合作用及转录因子维甲酸相关孤儿素受体γt（retinoic acid related orphan nuclear receptorm,ROR-γt）的协同诱导精细的调节下分化而来。其主要分泌的生物效应分子白细胞介素17（Interleukin17,IL-17）是一种促炎性反应细胞因子,在免疫和造血系统等发挥重要的作用。而器官移植排斥反应的本质就是炎性反应。因此深入研究Th-17细胞分化及其相关生物效应,有助认识其在器官移植排斥中的病理机制,也为治疗移植排斥反应提供新的靶点和途径。