Biomedical subjects

Joanne Yu

Publications and source records attributed to Joanne Yu.

4 recordsLinked to original sources

PubMed2006

Quantum dot semiconductor nanocrystals for immunophenotyping by polychromatic flow cytometry.

Immune responses arise from a wide variety of cells expressing unique combinations of multiple cell-surface proteins. Detailed characterization is hampered, however, by limitations in available probes and instrumentation. Here, we use the unique spectral properties of semiconductor nanocrystals (quantum dots) to extend the capabilities of polychromatic flow cytometry to resolve 17 fluorescence emissions. We show the need for this power by analyzing, in detail, the phenotype of multiple antigen-specific T-cell populations, revealing variations within complex phenotypic patterns that would otherwise remain obscure. For example, T cells specific for distinct epitopes from one pathogen, and even those specific for the same epitope, can have markedly different phenotypes. The technology we describe, encompassing the detection of eight quantum dots in conjunction with conventional fluorophores, should expand the horizons of flow cytometry, as well as our ability to characterize the intricacies of both adaptive and innate cellular immune responses.

CD3 Complex↗

PubMed2006

Tissue factor in cancer and angiogenesis: the molecular link between genetic tumor progression, tumor neovascularization, and cancer coagulopathy.

Tissue factor (TF), the primary cellular initiator of blood coagulation, is also involved in cancer-related processes such as hypercoagulability (Trousseau syndrome), tumor growth, angiogenesis, and metastasis. Indeed, elevated TF expression by cancer cells and their associated endothelial cells has been reported frequently. Oncogenic events in cancer cells (e.g., expression of mutant K- ras, EGFR, PTEN or p53) lead to an increase in TF levels and activity, and thereby promote tumor aggressiveness, angiogenesis, and hypercoagulability. Like TF, thrombin receptor (protease-activated receptor-1) is also upregulated in cancer cells expressing oncogenic K -ras. Pharmacological antagonists of some of these transforming genes (e.g., epidermal growth factor receptor inhibitors) could diminish TF expression, both locally and systemically, and hence these targeted agents could be viewed as potential indirect and cancer-specific anticoagulants, in addition to their direct antitumor effects. We postulate that levels of circulating TF may be useful in monitoring the biological activity of these agents. Although TF is essential for vascular development, its expression by tumor-associated endothelium appears to play a subtle and seemingly dispensable role. Thus, TF is a pivotal element of the tumor-vascular interface, is involved in many cancer-related processes, and may well constitute a promising new target for anticancer combination therapies in some disease settings.

Animals↗

PubMed2005

A live-cell assay to detect antigen-specific CD4+ T cells with diverse cytokine profiles.

Recently activated, but not resting, CD4(+) T cells express CD154, providing costimulatory signals to B cells and antigen-presenting cells (APCs). Therefore, de novo CD154 expression after stimulation identifies antigen-specific CD4(+) T cells. Previous assays were limited by the transient nature of surface CD154 expression; we overcame this by including fluorescently conjugated CD154-specific antibody during stimulation. Our assay is fully compatible with intracellular cytokine staining, and can be used for stimulations as long as 24 h. Notably, it is nonlethal, providing a means to purify viable antigen-specific CD4(+) T cells for further analysis. Using this assay, we found that stimulated cells expressing tumor necrosis factor (TNF)-alpha, interleukin (IL)-2 or interferon (IFN)-gamma were predominantly CD154(+). Furthermore, some cells expressing none of these cytokines also expressed CD154, suggesting that CD154 marks cells with other effector functions. For vaccine- or pathogen-specific responses, we found substantial heterogeneity in expression of CD154 and cytokines, suggesting previously unrecognized diversity in abilities of responding cells to stimulate APCs through CD40.

CD4 Antigens↗

PubMed2004

Vaccination in humans generates broad T cell cytokine responses.

In recent years, the quantification of T cell responses to pathogens or immunogens has become a common tool in the evaluation of disease pathogenesis or vaccine immunogenicity. Such measurements are usually limited to enumerating IFN-gamma-producing cells after ex vivo stimulation with Ag, but little is known about the phenotype or complete functional repertoire of the Ag-specific cells. We used 12-color flow cytometry to characterize Ag-specific T cells elicited by vaccines or natural infection to determine lineage and differentiation status as well as the capacity to produce four cytokines (IFN-gamma, TNF-alpha, IL-2, and IL-4) and a chemokine (MIP1beta). As expected, responding cells had a typical memory phenotype; however, the cytokine profiles associated with the responses were highly complex. The pattern of cytokine coexpression in response to specific Ags was a skewed subset of the complete repertoire (revealed by polyclonal stimulation). We found significant differences in the patterns of cytokines elicited by vaccination (where IFN-gamma was by far a subdominant response) vs natural infection; in addition, there was fairly significant intersubject variation. Our findings illustrate the limitation of the evaluation of immune responses using single functional measurements (such as IFN-gamma); in fact, it is likely that sensitive evaluation of Ag-specific T cells will require the coordinate measurement of several cytokines. The presence and variability of these complex response profiles introduce the possibility that selective functional expression patterns may provide correlates for vaccine efficacy or disease progression.

AIDS Vaccines↗