CD45R gives immunofluorescence and transduces signals on mouse T cells

Accelerator or Brake: Immune Regulators in Malaria

Malaria is a life-threatening infectious disease, affecting over 250 million individuals worldwide each year, eradicating malaria has been one of the greatest challenges to public health for a century. Growing resistance to anti-parasitic therapies and lack of effective vaccines are major contributing factors in controlling this disease. However, the incomplete understanding of parasite interactions with host anti-malaria immunity hinders vaccine development efforts to date. Recent studies have been unveiling the complexity of immune responses and regulators against Plasmodium infection. Here, we summarize our current understanding of host immune responses against Plasmodium-derived components infection and mainly focus on the various regulatory mechanisms mediated by recent identified immune regulators orchestrating anti-malaria immunity.

SYLARAS: A Platform for the Statistical Analysis and Visual Display of Systemic Immunoprofiling Data and Its Application to Glioblastoma

Accurately profiling systemic immune responses to cancer initiation and progression is necessary for understanding tumor surveillance and, ultimately, improving therapy. Here, we describe the SYLARAS software tool (systemic lymphoid architecture response assessment) and a dataset collected with SYLARAS that describes the frequencies of immune cells in primary and secondary lymphoid organs and in the tumor microenvironment of mice engrafted with a standard syngeneic glioblastoma (GBM) model. The data resource involves profiles of 5 lymphoid tissues in 48 mice and shows that GBM causes wide-spread changes in the local and systemic immune architecture. We use SYLARAS to identify a subset of CD45R/B220⁺ CD8⁺ T cells that is depleted from circulation but accumulates in the tumor mass and confirm this finding using multiplexed immunofluorescence microscopy. SYLARAS is freely available for download at (https://github.com/gjbaker/sylaras). A record of this paper’s transparent peer review process is included in the Supplemental Information.

Localized tumors such as glioblastoma alter the composition of the immune system in peripheral organs including the spleen, lymph nodes, bone marrow, and thymus. SYLARAS enables efficient, systematic analysis of immune system architecture across many organs and samples to reveal subtle, recurrent changes on a background of between-sample biological variability.

An optimized method for establishing high purity murine CD8+ T cell cultures

Establishing CD8(+) T cell cultures has been empirical and the published methods have been largely individual laboratory based. In this study, we optimized culturing conditions and show that IL-2 concentration is the most critical factor for the success of establishing CD8(+) T cell cultures. High IL-2 concentration encouraged T cells to non-specifically proliferate, express a B cell marker, B220, and undergo apoptosis. These cells also lose typical irregular T cell morphology and are incapable of sustaining long-term cultures. Using tetramer and intracellular cytokine assessments, we further demonstrated that many antigen-specific T cells have been rendered nonfunctional when expanded under high IL-2 concentration. When IL-2 is used in the correct range, B220-mediated cell depletion greatly enhanced the success rate of such T cell cultures.

T-lymphocytes enable osteoblast maturation via IL-17F during the early phase of fracture repair

While it is well known that the presence of lymphocytes and cytokines are important for fracture healing, the exact role of the various cytokines expressed by cells of the immune system on osteoblast biology remains unclear. To study the role of inflammatory cytokines in fracture repair, we studied tibial bone healing in wild-type and Rag1(-/-) mice. Histological analysis, µCT stereology, biomechanical testing, calcein staining and quantitative RNA gene expression studies were performed on healing tibial fractures. These data provide support for Rag1(-/-) mice as a model of impaired fracture healing compared to wild-type. Moreover, the pro-inflammatory cytokine, IL-17F, was found to be a key mediator in the cellular response of the immune system in osteogenesis. In vitro studies showed that IL-17F alone stimulated osteoblast maturation. We propose a model in which the Th17 subset of T-lymphocytes produces IL-17F to stimulate bone healing. This is a pivotal link in advancing our current understanding of the molecular and cellular basis of fracture healing, which in turn may aid in optimizing fracture management and in the treatment of impaired bone healing.

Non-HLDA8 animal homologue section anti-leukocyte mAbs tested for reactivity with equine leukocytes

In addition to the 379 monoclonal antibodies (mAbs) tested in the animal homologues section of HLDA8, another 155 mAbs were screened at the Institute for Zoo and Wildlife Research, Berlin for cross-reactivity with equine leukocytes. For this purpose, one colour flow-cytometric analysis was performed as screening test. This additional screening indicated further 16 mAbs as positive with staining homologous to human pattern, 1 mAb with weak (positive) reactivity, 11 mAbs with positive, but likely not valuable staining, 12 mAbs with alternate expression pattern from that expected from human immunology, 2 mAbs with questionable variable staining, 13 mAbs with weak-positive expression and alternate pattern, and 78 negative mAbs. In 23 cases, more appropriate target cells, such as thymocytes or stem cells, were not available for screening. The results support and add to the value of the "cross-reactivity" approach for equine immunology.

Expression of B220 on activated T cell blasts precedes apoptosis

Superantigens are bacterial or viral products that polyclonally activate T cells bearing certain TCR beta chain variable elements. For instance, Vbeta8+ T cells proliferate in response to staphylococcal enterotoxin B (SEB) in vivo and then undergo Fas- and/or TNF-mediated apoptosis. We have recently shown that apoptotic SEB-reactive T cells express the B cell marker B220. Here we report the identification of a novel subset of CD4+ B220+ T cell blasts that are the precursors of these apoptotic cells in SEB-immunized mice. Moreover, we show that the CD4- CD8- B220+ T cells that accumulate in the lymphoid organs of Fas ligand-defective gld mice stably express a form of the B220 molecule which exhibits biochemical similarities to that expressed by activated wild-type T cells, but is distinct from that displayed on the surface of B cells. Surprisingly, we also find a population of CD4+ B220+ pre-apoptotic T cells in FasL-defective gld mice, arguing that these cells can be generated in a Fas-independent fashion. Collectively, our data support a general model whereby upon activation, T cells up-regulate B220 before undergoing apoptosis. When the apoptotic mechanisms are defective, T cells presumably down-regulate their coreceptor molecules but retain expression of B220 as they accumulate in lymphoid organs.

Analysis of cytotoxic activity of the CD4+ T lymphocytes generated by local immunotherapy

We previously reported that the anti-tumour effect of OK-432 is considerably enhanced by its intratumoral injection together with fibrinogen. In the present study, we generated killer T cells by culturing tumour-infiltrating lymphocytes from thyroid cancer patients who had received this local immunotherapy. Phenotypic analysis revealed that the T cells were positive for CD3+, CD4+, Leu8-, CD45RO+ and T-cell receptor (TCR)alpha beta+, as well as showing strong surface expression of HLA-DR, CD25, LFA-1 and ICAM-1. The generated CD4+ T cells secreted interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, TNF-beta, and interleukin (IL)-6 (but not IL-4), and exhibited a high level of cytolytic activity against several tumour cell lines. The cytolytic activity of these T cells for Daudi cells was inhibited by preincubation with an anti-intercellular adhesion molecule (ICAM)-1 antibody, but not by preincubation with anti-TCR alpha beta, anti-CD2, or anti-LFA-1 antibodies. Pretreatment with anti-ICAM-1 antibody inhibited T-cell cytolytic activity, but not conjugation with target cells. In addition, incubation with immobilised anti-ICAM-1 enhanced the secretion of IFN-gamma by T cells. We conclude that ICAM-1 expressed on the effector cytotoxic CD4+ T lymphocytes delivers regulatory signals that enhance IFN-gamma secretion.

Activation of T cells through a T cell-specific epitope of CD45

The 180- and 190-kDa isoforms of CD45 are preferentially expressed on the helper inducer (memory) subset of CD4 cells. In order to generate monoclonal antibodies against the extracellular domains of these isoforms and determine whether they could regulate the function and activation of these cells, we developed a mAb, anti-4H2D, by immunizing Balb/c mice with an isogenic mouse pre-B cell line expressing the human 190-kDa CD45 isoform. Anti-4H2D reacts with approximately 60% of T cells, 70% of CD4 cells, and 60% of CD8 cells. The CD4 cell population defined by this mAb corresponds functionally and phenotypically to that defined by the CD45RO+CD29+ subset. Western blotting demonstrated that anti-4H2D reacts primarily with the 190-kDa isoform of CD45 and to a minor extent, the 205- and 180-kDa CD45 isoforms. Interestingly, this mAb reacted with only a subpopulation of mature thymocytes and peripheral T cells, despite the fact that the 190-kDa CD45 isoform, as well as CD45RO and CD29, is more widely distributed on cells of hematopoietic origin. The 4H2D epitope was neuraminidase sensitive, indicating that anti-4H2D reacts with a carbohydrate epitope which is present on only a subset of the T cells containing the 190-kDa CD45 isoform epitopes. Functional studies showed that soluble anti-4H2D augmented T cell proliferation induced by the CD2 and CD3 pathways, and treatment of T cells with this mAb up-regulated [Ca2+]i flux induced by both anti-CD2 and anti-CD3 mAbs. These results suggest that the 190-kDa CD45 isoform on human CD4 cells is heterogeneous and that the 190-kDa isoform recognized by anti-4H2D regulates the function and activation of CD4 helper T cells.

Stimulation of IFN-γ, TNF-α, and TNF-β secretion in IL-2-activated T cells: Costimulatory roles for LFA-1, LFA-2, CD44, and CD45 molecules

Lymphokine-activated killer (LAK) cells are peripheral blood lymphocytes (PBLs) that possess the ability to kill target cells in a non-major histocompatibility complex (MHC)-restricted manner. Both NK and T cells can be stimulated with interleukin-2 (IL-2) to become LAK cells. We previously reported that the interaction of LAK cells with tumor cells also induces the secretion of interferon-gamma (IFN-gamma). The NK subset of LAK (LAK-NK) cells is stimulated by tumor cells to secrete IFN-gamma in a non-MHC-restricted manner while the T cell subset of LAK (LAK-T) cells is stimulated to secrete IFN-gamma upon cross-linking of the T cell receptor (TCR)-CD3 complex. We here report that LAK-T cells stimulated with anti-CD3 mAbs and tumor cells secrete two additional cytokines, tumor necrosis factor-alpha (TNF-alpha) and TNF-beta/lymphotoxin (TNF-beta). In addition, we demonstrate that at least four other structurally unrelated molecules, in addition to the TCR-CD3 complex, on LAK-T cells participate in the stimulation of IFN-gamma, TNF-alpha, and TNF-beta production. These molecules are the lymphocyte function associated antigen-1 (LFA-1), lymphocyte function associated antigen-2 (LFA-2), CD44, and CD45. LFA-1 is an integrin, LFA-2 is a member of the immunoglobulin supergene family, CD44 is homologous to the cartilage link proteins, and CD45 is a tyrosine phosphatase. Ligands to three of these molecules have been identified; ICAM-1, LFA-3, and hyaluronic acid binding to LFA-1, LFA-2, and CD44, respectively. LFA-1, LFA-2, and CD44 are reported to function both as adhesion molecules and as costimulators in resting T cells. Our data suggest that these three molecules enhance IFN-gamma, TNF-alpha, and TNF-beta production by augmenting LAK-T cell to tumor cell adhesion and also by functioning as costimulators.

Differing effects of delta-9-tetrahydrocannabinol (THC) on murine spleen cell populations dependent upon stimulators

Delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, can suppress the immune response, both in vitro and in vivo. In the present study, THC was found to either up-regulate or down-regulate lymphocytes depending on the method of stimulation. When the mitogens concanavalin A (Con A) or phytohemagglutinin (PHA) were used to stimulate THC-treated splenocytes, a down-regulation of lymphocyte proliferation occurred, which reflected lower T-cell numbers in general and Ly2 positive cells specifically. When splenocytes were stimulated directly by using anti-CD3 antibody it was found that low concentrations of THC enhanced lymphocyte proliferation, T-cell numbers in general, and Ly2 cells specifically. These results emphasize that THC can either enhance or suppress aspects of the immune response, depending on the specific immune stimulants used and the specific parameter of immunity measured.

Immunological memory in T cells

CD4 and CD8 T lymphocytes can be further subdivided using antibodies to isoforms of CD45 with restricted cellular distributions. These further subsets, detected in man, rodents and sheep, differ in surface phenotypes, rate of cycling, migration and response to recall antigens. Their lineage relationship has still not been fully established.

Differential expression of the alternatively spliced exons of murine CD45 in Th1 and Th2 cell clones

Antigen-specific murine CD4+ T cell clones can be divided into functionally distinct subsets known as Th1 and Th2. To date these cells have been indistinguishable by surface phenotype. This report identifies two anti-CD45R monoclonal antibodies (14.8 and C363.16A) that bind preferentially to Th2 cells. Further analysis of the CD45-specific mRNA in Th1 and Th2 cells shows clear differences between these two cell types. Th1 cell clones express mRNA for the two smallest forms of CD45 containing none or only one of the alternatively splices exons. In contrast, Th2 cell clones express predominantly the high molecular weight isoforms of CD45 containing two or three of the alternatively spliced exons.

Evidence that the CD45 phosphatase regulates the activity of the phospholipase C in mouse T lymphocytes

The importance of the tyrosine phosphatase CD45 in the regulation of lymphocyte activation was first demonstrated using antibodies against the extracellular domain of CD45 in functional assays. More recently it was reported that CD45-negative mutants were nonresponsive to stimulation through the T cell receptor-CD3 complex. We have studied the effect of CD45 cross-linking on the early signals induced by CD3 in mouse T cells. We show that CD45 cross-linking inhibits the increase in inositol phosphates and cytoplasmic Ca2+ induced by cross-linking of CD3. This indicates that CD45 is involved in the regulation of phospholipase C.

Molecular associations on the T cell surface correlate with immunological memory

Different isoforms of CD45 are expressed on naive and memory CD4 T cells in the mouse, as revealed by an antibody to a set of isoforms of CD45 that utilize exon B, called CD45RB. Cloned TH1 and TH2 lines also differ for expression of isoforms detected by this antibody. Differential expression of CD45 isoforms correlates with different behavior of cell surface molecules involved in transmembrane signal transduction. On naive T cells, CD4, CD45 and the CD3/T cell receptor complex behave as independent entities. On memory T cells, these three molecules are stably associated on the T cell surface. Furthermore, on TH2 cells, which express intermediate levels of CD45RB, CD4 is stably associated with CD45 isoforms other than CD45RB, but this complex is not associated with the CD3/T cell receptor. These results lead us to propose that immunological memory in CD4 T cells consists of an altered structure of the T cell's specific signal transduction apparatus controlled by low-molecular weight CD45 isoforms. This altered receptor structure would allow the more sensitive triggering of the T cell characteristic of memory cells. The organization of multimolecular signal transduction systems may be a general means by which cells alter their physiological behavior, allowing the acquisition of new phenotypic characteristics.

Intimate association of Thy-1 and the T-cell antigen receptor with the CD45 tyrosine phosphatase

Immunoprecipitation of Thy-1 from Triton X-100 detergent lysates of surface-iodinated and chemically cross-linked T cells precipitated at least five major and discrete bands. Four of these bands were identified as Thy-1, CD45 (a transmembrane tyrosine phosphatase), a major histocompatibility complex-encoded class I molecule, and beta 2-microglobulin. Similar analyses revealed that CD45 was coprecipitated from lysates of cross-linker-treated cells by antibodies to the T-cell antigen receptor (TCR). The same pattern of coprecipitated bands was observed when digitonin was used to lyse untreated cells. Immunoprecipitation of Thy-1 or the TCR from lysates of cross-linked T cells precipitated CD45 tyrosine phosphatase activity. Calculations based upon the amounts of coprecipitated enzymatic activity or TCR zeta chain indicate that a substantial fraction of Thy-1 and TCR complexes can be cross-linked to CD45. These data support a model in which the dependence of Thy-1 signaling on TCR coexpression is due to their common interaction with a tyrosine phosphatase and provide a possible structural basis for the influence of CD45 on TCR-mediated signaling.

Anti-CD45RA antibodies increase the proliferation of mouse T cells to phytohemagglutinin through the interleukin 2/interleukin 2 receptor pathway

We have studied the effect of anti-CD45RA monoclonal antibodies on the proliferation of murine spleen T cells activated with phytohemagglutinin. Antibodies act on both CD8 and CD4 subsets of T cells. They seem to replace a signal normally delivered by accessory cells which would act through the interleukin 2/interleukin 2 receptor pathway.

The role of cell surface recognition structures in the initiation of MHC-unrestricted 'promiscuous' killing by T cells

CD3+ T cells mediate relatively promiscuous patterns of major histocompatibility complex (MHC)-unrestricted target cell lysis following activation. Cell-cell contact between target and effector cells is essential in this form of cytotoxicity. Although the T-cell receptor (TCR)-CD3 molecular complex can transmit signals that initiate MHC unrestricted T-cell killing, recognition of targets by the TCR is not essential for this form of cytotoxicity. In this review by Dwain Thiele and Peter Lipsky, a model of the triggering of T cells to effect MHC-unrestricted cytotoxicity is proposed.

T cells in transplantation immunity

This paper reviews the following problems in transplantation immunity: (i) short-lived ability to transfer immunity or suppression, in contrast to long-lived immunological memory in the autochthonous animal; (ii) short-lived ability to transfer graft-resistance, in contrast to long-lived ability to transfer helper activity for B-cells; (iii) the response to H-Y, as a system that might solve some outstanding problems in antigen presentation; and (iv) the contrast between live and killed allogeneic cells as immunogens. All of these problems, it is suggested, are amenable to study by modern methods. Students like me were drawn into Peter Medawar's orbit in the 1940s and 1950s by an irresistible mix of intellectual challenge and the glamour of experimental surgery. Much the same was happening elsewhere in the laboratories of Ray Owen, Milan Hasek, George Snell, Burnet, and Florey, and by 1960 the transplantation immunologists could justly claim to have opened up a whole new area of ideas in biology: we had discovered the lymphocyte as the antigen-sensitive cell, and the principles of immunological tolerance; we had revived interest in cellular immunity, and it was we who found the MHC (even if we had little idea of its real meaning). But by 1960 the first wave of success had passed, and the penetration of immunology by molecular biology had begun. Interest in transplantation immunity perceptibly declined, although many groups continued to address important problems, particularly in the field of organ transplantation. (ABSTRACT TRUNCATED AT 250 WORDS)

A monoclonal antibody to murine CD45R distinguishes CD4 T cell populations that produce different cytokines

CD4 T cell clones have been shown to be functionally heterogeneous in the mouse. However, it is not known if normal CD4 T cells are also functionally heterogeneous, or whether functional specialization is a result of cloning and long-term culture. To approach this question, a monoclonal antibody reacting with a subset of CD4 T cells has been prepared by immunization of rats with different cloned T cell lines all sharing the same functional activity. This monoclonal antibody reacts with a subset of CD45 (T200) molecules by binding to a determinant requiring the expression of the second variable exon of the CD45 molecule. Some CD4 T cells bear high levels of this marker, while others react only weakly. This antibody was used to separate CD4 T cells into two subpopulations. The brightly staining population was found to produce interleukin (IL) 2 and not IL 4, while the weakly staining population produced IL 4 and not IL 2. These data demonstrate that CD4 T cells in normal mice are already functionally committed, and that they differentially express forms of CD45 that contain the second variable exon.