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Thomas T Su

Publications and source records attributed to Thomas T Su.

7 recordsLinked to original sources
PubMed2004

Protein kinase C family functions in B-cell activation.

Members of the protein kinase C (PKC) family play important but distinct roles in B-cell activation, as demonstrated by emerging genetic and biochemical studies. PKCbeta is indispensable for B-cell antigen receptor (BCR)-induced NF-kappaB activation and B-cell survival. Recent evidence indicates that PKCbeta might regulate inhibitor of kappaB kinase (IKK) and NF-kappaB activation through interaction with the CARMA1/Bcl10/MALT signaling complex in BCR microdomains. By contrast, the novel PKC isoform PKCdelta is specifically required to maintain the tolerance of self-reactive B cells.

Animals↗
PubMed2004

Signaling in transitional type 2 B cells is critical for peripheral B-cell development.

Splenic peripheral B-cell development and the events regulating this functionally significant but relatively poorly defined developmental process have become a major focus in recent studies in B-cell immunology. Following the exit from the bone marrow, peripheral B cells develop through transitional type 1 (T1) and transitional type 2 (T2) B-cell stages. Emerging data suggest that the T2 subset is the immediate precursor of the mature B-cell populations present in the spleen. In this review, we first elaborate on the evidence describing the unique properties of CD21hiCD24hiCD23hiIgMhiIgDhi T2 B cells. T2 cells uniquely activate a proliferative, pro-survival, and differentiation program in response to B-cell antigen receptor (BCR) engagement. The potential mechanisms leading to the differential BCR responsiveness of T1 versus T2 B cells are discussed. We also review evidence that distinguishes key BCR-dependent signaling pathways operative in T2 and mature B cells. These signaling cascades include a protein kinase Cbeta (PKCbeta)-dependent cell-survival pathway and a second PKCbeta-independent pathway essential for BCR-driven differentiation. Finally, we discuss recent intriguing results suggesting that the type of signal(s) encountered by T2 cells leads to their differential maturation toward the follicular mature versus marginal zone mature B-cell populations. These combined observations suggest important implications with regard to B-cell selection and tolerance, potential novel therapeutic targets for B-cell lymphomas, and how the intricate balance of commensal organisms and other microenvironmental signals interact to promote the generation of 'innate-like' versus adaptive effector B-cell populations.

Animals↗
PubMed2004

Objective changes in brow position, superior palpebral crease, peak angle of the eyebrow, and jowl surface area after volumetric radiofrequency treatments to half of the face.

BACKGROUND: Radiofrequency application through a proprietary device has recently been used for facial tissue tightening. Uniform volumetric heating of the dermis is created by passage of electrical current, while protection of the epidermis is maintained by concurrent cryogen cooling. OBJECTIVE: To objectively quantify the effectiveness of volumetric radiofrequency application on the face, we treated 10 patients on the left side of the face with radiofrequency and evaluated the changes in brow position, superior palpebral crease, angle of the eyebrow, and jowl surface area. METHODS: Uniform treatments were applied at 134 J/cm(2) to the left side of the forehead and 1 cm past midline, at 115 J/cm(2) to the left side of temple and cheeks, and at 97 J/cm(2) to the left side of the jaw line and inferior postauricular surface. Patients were evaluated at monthly intervals up to 3 months with digital photography. Morphologic changes were evaluated with the "measuring tool" and "angle tool" of the Mirror Suite imaging system for aligned frontal-view photographs (for eyebrow position, superior palpebral crease elevation, and eyebrow angle changes) and the "outline tool" for aligned oblique-view photographs (for jowl surface area changes). RESULTS: At the end of 3 months on the side that was treated, patients exhibited on average 4.3 mm of brow elevation and 1.9 mm of superior palpebral crease elevation along the midpupillary line and an average of 2.4 mm of brow elevation along the lateral canthal line. There was no significant improvement of brow elevation along the lateral canthal line on the contralateral side. The peak angle of the ipsilateral eyebrow became slightly more acute by an average of 4.5 degrees after treatments. Moreover, the jowls on the lower part of the face, displayed a mean decrease of 22.6% in surface area after treatments. The nontreated side displayed a lack of eyebrow angle and jowl surface area changes. CONCLUSIONS: The application of radiofrequency to the face provides quantifiable changes. The brow along the midpupillary line is elevated to a greater degree than the lateral brow. This is consistent with acute angle changes seen in the eyebrow. Improvements in the lower part of the face with radiofrequency application can be quantified by demonstrating a decrease jowl surface. Moreover, these measurement techniques can be useful tools for evaluating other treatment parameters with radiofrequency application.

Adult↗
PubMed2002

Dysregulated TCL1 promotes multiple classes of mature B cell lymphoma.

The TCL1 protooncogene is overexpressed in many mature B cell lymphomas, especially from AIDS patients. To determine whether aberrant expression promotes B cell transformation, we generated a murine model in which a TCL1 transgene was overexpressed at similar levels in both B and T cells. Strikingly, transgenic mice developed Burkitt-like lymphoma (BLL) and diffuse large B cell lymphoma (DLBCL) with attendant Bcl-6 expression and mutated J(H) gene segments at a very high penetrance beginning at 4 months of age. In contrast, only one mouse developed a T cell malignancy at 15 months, consistent with a longer latency for transformation of T cells by TCL1. Activation of premalignant splenic B cells by means of B cell antigen receptor (BCR) engagement resulted in significantly increased proliferation and augmented AKT-dependent signaling, including increased S6 ribosomal protein phosphorylation. Transgenic spleen cells also survived longer than wild-type spleen cells in long-term culture. Together these data demonstrate that TCL1 is a powerful oncogene that, when overexpressed in both B and T cells, predominantly yields mature B cell lymphomas.

Animals↗
PubMed2002

PKC-beta controls I kappa B kinase lipid raft recruitment and activation in response to BCR signaling.

NF-kappa B signaling is required for the maintenance of normal B lymphocytes, whereas dysregulated NF-kappa B activation contributes to B cell lymphomas. The events that regulate NF-kappa B signaling in B lymphocytes are poorly defined. Here, we demonstrate that PKC-beta is specifically required for B cell receptor (BCR)-mediated NF-kappa B activation. B cells from protein kinase C-beta (PKC-beta)-deficient mice failed to recruit the I kappa B kinase (IKK) complex into lipid rafts, activate IKK, degrade I kappa B or up-regulate NF-kappa B-dependent survival signals. Inhibition of PKC-beta promoted cell death in B lymphomas characterized by exaggerated NF-kappa B activity. Together, these data define an essential role for PKC-beta in BCR survival signaling and highlight PKC-beta as a key therapeutic target for B-lineage malignancies.

Animals↗
PubMed2002

Transitional B lymphocyte subsets operate as distinct checkpoints in murine splenic B cell development.

Signaling through the Ag receptor is required for peripheral B lymphocyte maturation and maintenance. Defects in components of the B cell receptor (BCR) signalosome result in developmental blocks at the transition from immature (heat-stable Ag (HSA)(high)) to mature (HSA(low)) B cells. Recent studies have subdivided the immature, or transitional, splenic B cells into two subsets, transitional 1 (T1) and transitional 2 (T2) cells. T1 and T2 cells express distinct surface markers and are located in distinct anatomic locations. In this report, we evaluated the BCR signaling capacity of T1 and T2 B cell subsets. In response to BCR engagement, T2 cells rapidly entered cell cycle and resisted cell death. In contrast, T1 cells did not proliferate and instead died after BCR stimulation. Correlating with these results, T2 cells robustly induced expression of the cell cycle regulator cyclin D2 and the antiapoptotic factors A1/Bfl-1 and Bcl-x(L) and exhibited activation of Akt. In contrast, T1 cells failed to up-regulate these markers. BCR stimulation of T2 cells also led to down-regulation of CD21 and CD24 (HSA) expression, resulting in a mature B cell phenotype. In addition, T2 cells from Bruton's tyrosine kinase-deficient Xid mice failed to generate these proliferative and survival responses, suggesting a requirement for the BCR signalosome specifically at the T2 stage. Taken together, these data clearly demonstrate that T2 immature B cells comprise a discrete developmental subset that mediates BCR-dependent proliferative, prosurvival, and differentiation signals. Their distinct BCR-dependent responses suggest unique roles for T1 vs T2 cells in peripheral B cell selection.

Agammaglobulinaemia Tyrosine Kinase↗