Costimulation of naive human CD4 T cells through intercellular adhesion molecule-1 promotes differentiation to a memory phenotype that is not strictly the result of multiple rounds of cell division

ICAMs in Immunity, Intercellular Adhesion and Communication

Interactions among leukocytes and leukocytes with immune-associated auxiliary cells represent an essential feature of the immune response that requires the involvement of cell adhesion molecules (CAMs). In the immune system, CAMs include a wide range of members pertaining to different structural and functional families involved in cell development, activation, differentiation and migration. Among them, β2 integrins (LFA-1, Mac-1, p150,95 and αDβ2) are predominantly involved in homotypic and heterotypic leukocyte adhesion. β2 integrins bind to intercellular (I)CAMs, actin cytoskeleton-linked receptors belonging to immunoglobulin superfamily (IgSF)-CAMs expressed by leukocytes and vascular endothelial cells, enabling leukocyte activation and transendothelial migration. β2 integrins have long been viewed as the most important ICAMs partners, propagating intracellular signalling from β2 integrin-ICAM adhesion receptor interaction. In this review, we present previous evidence from pioneering studies and more recent findings supporting an important role for ICAMs in signal transduction. We also discuss the contribution of immune ICAMs (ICAM-1, -2, and -3) to reciprocal cell signalling and function in processes in which β2 integrins supposedly take the lead, paying particular attention to T cell activation, differentiation and migration.

Recent Advances in Camel Immunology

Camels are domesticated animals that are highly adapted to the extreme desert ecosystem with relatively higher resistance to a wide range of pathogens compared to many other species from the same geographical region. Recently, there has been increased interest in the field of camel immunology. As the progress in the analysis of camel immunoglobulins has previously been covered in many recent reviews, this review intends to summarize published findings related to camel cellular immunology with a focus on the phenotype and functionality of camel leukocyte subpopulations. The review also describes the impact of different physiological (age and pregnancy) and pathological (e.g. infection) conditions on camel immune cells. Despite the progress achieved in the field of camel immunology, there are gaps in our complete understanding of the camel immune system. Questions remain regarding innate recognition mechanisms, the functional characterization of antigen-presenting cells, and the characterization of camel NK and cytotoxic T cells.

CD4+ T cell activation and associated susceptibility to HIV-1 infection in vitro increased following acute resistance exercise in human subjects

Early studies in exercise immunology suggested acute bouts of exercise had an immunosuppressive effect in human subjects. However, recent data, show acute bouts of combined aerobic and resistance training increase both lymphocyte activation and proliferation. We quantified resistance exercise-induced changes in the activation state of CD4+ T lymphocytes via surface protein expression and using a medically relevant model of infection (HIV-1). Using a randomized cross-over design, 10 untrained subjects completed a control and exercise session. The control session consisted of 30-min seated rest while the exercise session entailed 3 sets × 10 repetitions of back squat, leg press, and leg extensions at 70% 1-RM with 2-min rest between each set. Venous blood samples were obtained pre/post each session. CD4+ T lymphocytes were isolated from whole blood by negative selection. Expression of activation markers (CD69 & CD25) in both nonstimulated and stimulated (costimulation through CD3+ CD28) cells were assessed by flow cytometry. Resistance exercised-induced effects on intracellular activation was further evaluated via in vitro infection with HIV-1. Nonstimulated CD4+ T lymphocytes obtained postexercise exhibited elevated CD25 expression following 24 h in culture. Enhanced HIV-1 replication was observed in cells obtained postexercise. Our results demonstrate that an acute bout of resistance exercise increases the activation state of CD4+ T lymphocytes and results in a greater susceptibility to HIV-1 infection in vitro. These findings offer further evidence that exercise induces activation of T lymphocytes and provides a foundation for the use of medically relevant pathogens as indirect measures of intracellular activation.

Coreceptors and Their Ligands in Epithelial γδ T Cell Biology

Epithelial tissues line the body providing a protective barrier from the external environment. Maintenance of these epithelial barrier tissues critically relies on the presence of a functional resident T cell population. In some tissues, the resident T cell population is exclusively comprised of γδ T cells, while in others γδ T cells are found together with αβ T cells and other lymphocyte populations. Epithelial-resident γδ T cells function not only in the maintenance of the epithelium, but are also central to the repair process following damage from environmental and pathogenic insults. Key to their function is the crosstalk between γδ T cells and neighboring epithelial cells. This crosstalk relies on multiple receptor–ligand interactions through both the T cell receptor and accessory molecules leading to temporal and spatial regulation of cytokine, chemokine, growth factor, and extracellular matrix protein production. As antigens that activate epithelial γδ T cells are largely unknown and many classical costimulatory molecules and coreceptors are not used by these cells, efforts have focused on identification of novel coreceptors and ligands that mediate pivotal interactions between γδ T cells and their neighbors. In this review, we discuss recent advances in the understanding of functions for these coreceptors and their ligands in epithelial maintenance and repair processes.

MHC class II associated stomach cancer mutations correlate with lack of subsequent tumor development

The role of tumor cell expression of major histocompatibility class II (MHCII) has been controversial, with evidence indicating that tumor cell expression of MHCII may lead to an anti-tumor immune response and to tumor cell apoptosis and that MHCII has pro-tumorigenic functions. The cancer genome atlas (TCGA) indicates numerous deleterious mutations for the highly specific, MHCII transcriptional activation proteins, RFX5, RFXAP, RFXANK and CIITA. Also, mutations in the non-polymorphic, human leukocyte antigen (HLA)-DRA gene, which encodes the heavy chain for the most prominent human MHCII molecule, HLA-DR, are common. For many, if not most TCGA cancer datasets, the MHCII specific mutations do not associate with clinical outcomes. However, stomach carcinoma represents an exception, where the data indicate that MHCII-specific mutations are associated with a more favorable outcome. These data raise the question of whether stomach cancer mutations represent effective haploinsufficiency or whether mutations that are associated with a favorable outcome occur with other stomach cancer molecular features that limit the function of the two alleles that represent these MHCII-related proteins.

Regulatory T-cell development and function are impaired in mice lacking membrane expression of full length intercellular adhesion molecule-1

To further investigate the contribution of intercellular adhesion molecule-1 (ICAM-1) to adaptive immune responses, we analysed T-cell development and function in mice lacking full-length ICAM-1 (ICAM-1(tm1Jcgr) ). Compared with wild-type (ICAM-1(WT) ) mice, ICAM-1(tm1Jcgr) mice have impaired thymocyte development. Proportions and numbers of double negative, double positive, mature CD4(+) and CD8(+) thymocytes, as well as of regulatory T (Treg) cells were also significantly decreased. In the periphery, ICAM-1(tm1Jcgr) mice had significantly decreased proportions and numbers of naive and activated/memory CD4(+) and CD8(+) T cells, as well as of Treg cells, in lymph nodes but not in the spleen. In vitro activation of CD4(+) and CD8(+) T cells from ICAM-1(tm1Jcgr) mice with anti-CD3 antibodies and antigen-presenting cells (APCs) resulted in a significantly weaker proliferation, whereas proliferation induced with anti-CD3 and anti-CD28 antibody-coated beads was normal. In vivo immunization of ICAM-1(tm1Jcgr) mice resulted in normal generation of specific effector and memory immune responses that protect against a viral challenge. However, contrary to ICAM-1(WT) mice, immunization-induced specific effectors could not eradicate immunogen-expressing tumours. Treg cells from ICAM-1(tm1Jcgr) mice have abnormal activation and proliferation induced by anti-CD3 antibody and APCs, and have markedly decreased suppressive activity in vitro. In contrast to ICAM-1(WT) mice, they were unable to control experimentally induced colitis in vivo. Hence, our results further highlight the pleiotropic role of ICAM-1 in T-cell-dependent immune responses, with a major role in Treg cell development and suppressive function.

ICAM-1-dependent homotypic aggregates regulate CD8 T cell effector function and differentiation during T cell activation

A hallmark of T cell activation in vitro and in vivo is the clustering of T cells with each other via interaction of the LFA-1 integrin with ICAM-1. The functional significance of these homotypic aggregates in regulating T cell function remains unknown. We used an APC-free in vitro activation system to demonstrate that stimulation of purified naive CD8 T cells results in enhanced expression of ICAM-1 on T cells that is sustained by the inflammatory cytokine IL-12 and associated with robust T cell aggregates. ICAM-1-deficient CD8 T cells proliferate normally but demonstrate a striking failure to aggregate. Interestingly, loss of ICAM-1 expression results in elevated levels of IFN-γ and granzyme B, as well as enhanced cytotoxicity. Similar results were obtained when anti-LFA-1 Ab was used to block the clustering of wild-type T cells. ICAM-1 ligation is not required for IFN-γ regulation, as clustering of ICAM-1-deficient CD8 T cells with wild-type T cells reduces IFN-γ expression. Analysis using a fluorescent reporter that monitors TCR signal strength indicates that T cell clustering limits T cell exposure to Ag during activation. Furthermore, T cell clustering promotes the upregulation of the CTLA-4 inhibitory receptor and the downregulation of eomesodermin, which controls effector molecule expression. Activation of ICAM-1-deficient CD8 T cells in vivo results in an enhanced percentage of KLRG-1(+) T cells indicative of short-lived effectors. These results suggest that T cell clustering represents a mechanism that allows continued proliferation but regulates T cell effector function and differentiation.

Expressional time phase of leukocyte molecules induced by allogenic cardiac antigen and cyclosporin A in rats' in vitro model

The immunosuppressive agent cyclosporin A has been proven to reduce the rejection rate and prolong the survival time of transplanted hearts. But some reports showed that cyclosporine A did not completely suppress the rejection. We performed in vitro studies to model a time course to observe the effect of cyclosporin A.

METHODS

The experiment was divided into a control group (group I), an antigen group (group II), a cyclosporin A group (group III) and an antigen + cyclosporin A group (group IV). After transplantation, at 2 h, 6 h, 12 h, 24 h, 48 h and 72 h, leukocyte molecules were monitored.

RESULTS

The expression of IL-2R peaked at 12 h in group II and at 6 h in group III. There was a gradual decline in the expression of the P59 gene in group I, positive expression at 2 h and between 12 h and 24 h in group II, in group IV, there was a decrease at 48 h. The expression of the CD4 gene was lowest at 2 h in group I and at 6 h in group II. CD4 expression then quickly increased to a maximum at 48 h in group III, at 2 h in group IV. There was a minimal expression was reached at 12 h in group I and IV and at 6 h in group III in the expression of the CD8 gene.

CONCLUSIONS

Alloantigen induced lymphocytes to release IL-2R and P59 and stimulated the induction of the CD4 gene' transcription for 6 h. Cyclosporin A stimulated the release of IL-2R for 2 h. These results provide an in vitro basis for describing the time phases of rejection inhibited by cyclosporin A.

Elimination of T cell reactivity to pancreatic β cells and partial preservation of β cell activity by peptide blockade of LFA-1:ICAM-1 interaction in the NOD mouse model

In insulin dependent diabetes mellitus (T1D), self-reactive T cells infiltrate pancreatic islets and induce beta cell destruction and dysregulation of blood glucose. A goal is to control only the self-reactive T cells, leaving the remainder of the T cell population free to protect the host. One approach is blockade of the second signal for T cell activation while allowing the first (antigen-specific) signal to occur. This work proposes that small peptides that block interaction of second signals delivered through the counter receptors LFA-1:ICAM-1 will induce attacking T cells (receiving the antigen signal) to become anergic or undergo apoptosis. In NOD mice, the peptides eliminated T cell reactivity against pancreatic antigens and reduced cellular infiltration into islets, which retained stronger density of insulin staining at five weeks after cessation of therapy. In in vitro studies the peptides induced nonresponsiveness during activation of T cells from mice and from human peripheral blood.

Choice of resident costimulatory molecule can influence cell fate in human naïve CD4+ T cell differentiation

With antigen stimulation, naïve CD4+ T cells differentiate to several effector or memory cell populations, and cytokines contribute to differentiation outcome. Several proteins on these cells receive costimulatory signals, but a systematic comparison of their differential effects on naïve T cell differentiation has not been conducted. Two costimulatory proteins, CD28 and ICAM-1, resident on human naïve CD4+ T cells were compared for participation in differentiation. Under controlled conditions, and with no added cytokines, costimulation through either CD3+CD28 or CD3+CAM-1 induced differentiation to T effector and T memory cells. In contrast, costimulation through CD3+ICAM-1 induced differentiation to Treg cells whereas costimulation through CD3+CD28 did not.

A unique subset of CD4+CD25highFoxp3+ T cells secreting interleukin-10 and transforming growth factor-beta1 mediates suppression in the tumor microenvironment

PURPOSE

Immunosuppression, including that mediated by CD4(+)CD25(high)Foxp3(+) regulatory T cells (Treg), is a characteristic feature of head and neck squamous cell carcinoma (HNSCC). Tregs with a distinct phenotype in tumor-infiltrating lymphocytes (TIL) contribute to local immune suppression.

EXPERIMENTAL DESIGN

The frequency and phenotype of Treg in TIL and/or peripheral blood mononuclear cells (PBMC) in 15 HNSCC patients and PBMC in 15 normal controls were compared. Single-cell sorted CD4(+)CD25(high) T cells were tested for regulatory function by coculture with carboxyfluorescein diacetate succinimidyl ester-labeled and activated autologous CD4(+)CD25(-) responder T cells. Transwell inserts separating Treg from responders and neutralizing interleukin-10 (IL-10) or transforming growth factor-beta1 (TGF-beta1) antibodies were used to evaluate the mechanisms used by Treg to suppress responder cell proliferation.

RESULTS

In TIL, CD25(+) cells were enriched in the CD3(+)CD4(+) subset (13 +/- 3%) relative to circulating CD3(+)CD4(+) T cells (3 +/- 0.7%) in HNSCC patients (P < or = 0.01) or normal controls (2 +/- 1.5%; P < or = 0.001). Among the CD3(+)CD4(+) subset, CD25(high) Treg represented 3 +/- 0.5% in TIL, 1 +/- 0.3% in PBMC, and 0.4 +/- 0.2% in normal controls. Tregs in TIL were GITR(+), IL-10(+), and TGF-beta1(+), although circulating Treg up-regulated CD62L and CCR7 but not GITR, IL-10, or TGF-beta1. Treg in TIL mediated stronger suppression (P < or = 0.001) than Treg in PBMC of HNSCC patients. The addition of neutralizing IL-10 and TGF-beta antibodies almost completely abrogated suppression (5 +/- 2.51%). Transwell inserts partly prevented suppression (60 +/- 5% versus 95 +/- 5%).

CONCLUSIONS

Suppression in the tumor microenvironment is mediated by a unique subset of Treg, which produce IL-10 and TGF-beta1 and do not require cell-to-cell contact between Treg and responder cells for inhibition.