Biomedical subjects

Mauro Tolaini

Publications and source records attributed to Mauro Tolaini.

7 recordsLinked to original sources

PubMed2006

Do CD8 effector cells need IL-7R expression to become resting memory cells?

The role for IL-7R expression in the differentiation of effector T cells into resting memory remains controversial. Here, using a conditional IL-7R transgenic model, we were able to test directly whether CD8 effector T cells require IL-7R expression for their differentiation into resting memory cells. In the absence of IL-7R expression, effector cells transferred into "full" hosts underwent a protracted and unremitting contraction compared with IL-7R-expressing control cells and were unable to develop into long-term resting memory cells. Surprisingly, when the same effector cells were transferred into empty T-cell-deficient hosts, they could generate long-lived fully functional resting memory cells independently of IL-7R expression. Formation of these latter cells was found to be dependent on IL-15, because the same IL-7R-deficient effector cells were rapidly lost from IL-15-deficient hosts, having a half-life of less than 40 hours. Therefore, our data suggest that, under physiological conditions, both IL-7 and IL-15 synergize to promote the formation of memory cells directly by limiting the contraction of effectors that occurs following an immune response and that reexpression of IL-7R is a key checkpoint in the regulation of this process.

Adoptive Transfer↗

PubMed2005

Human high mobility group box transcription factor 1 affects thymocyte development and transgene variegation.

It has been shown previously that a human CD2 (hCD2) disabled locus control region (LCR) transgene is unable to establish an open chromatin configuration in all the T cells, and this leads to position effect variegation of the transgene. In this study we show that thymus-specific overexpression of human high mobility group box transcription factor 1 (HBP1), a transcription factor that binds a specific sequence within the hCD2 LCR, affects thymus cellularity as well as the number of CD8(+) thymocytes in two independent transgenic mouse lines and increases the proportion of T cells that fully activate the transgenic locus in hCD2 variegating mice in a sequence-specific dependent manner. This finding suggests that overexpression of HBP1 can affect lineage commitment and can relieve the suppressive influence of heterochromatin, allowing thymocytes to express the variegating target locus more efficiently. These effects could be the result of direct HBP1 action on LCR activity. Alternatively, the extra HBP1 molecules may sequester repressive elements away from the LCR, thus allowing transcription permissive states to form on the transgene locus.

Animals↗

PubMed2003

L-selectin shedding does not regulate constitutive T cell trafficking but controls the migration pathways of antigen-activated T lymphocytes.

L-selectin mediates rolling of lymphocytes in high endothelial venules (HEVs) of peripheral lymph nodes (PLNs). Cross-linking of L-selectin causes proteolytic shedding of its ectodomain, the physiological significance of which is unknown. To determine whether L-selectin shedding regulates lymphocyte migration, a mutant form that resists shedding (LdDeltaP-selectin) was engineered. Transgenic mice expressing either LDeltaP or wild-type (WT) L-selectin on T cells were crossed with L-selectin knockout (KO) mice. The cellularity and subset composition of secondary lymphoid organs did not differ between LDeltaP and WT mice, however, they were different from C57BL/6. Plasma levels of soluble L-selectin in LDeltaP mice were reduced to <5% of WT and C57BL/6 mice. The rolling properties of T lymphocytes from LDeltaP and WT mice on immobilized L-selectin ligands were similar. Furthermore, similar numbers of LDeltaP and WT T lymphocytes were recruited from the bloodstream into PLNs in mice, although LDeltaP T cells transmigrated HEVs more slowly. WT, but not LDeltaP-selectin, underwent rapid, metalloproteinase-dependent shedding after TCR engagement, and LDeltaP T cells retained the capacity to enter PLNs from the bloodstream. These results suggest that the ability to shed L-selectin is not required for T cell recirculation and homing to PLNs. However, L-selectin shedding from antigen-activated T cells prevents reentry into PLNs.

Animals↗

PubMed2003

Killer cell Ig-like receptor and leukocyte Ig-like receptor transgenic mice exhibit tissue- and cell-specific transgene expression.

To generate an experimental model for exploring the function, expression pattern, and developmental regulation of human Ig-like activating and inhibitory receptors, we have generated transgenic mice using two human genomic clones: 52N12 (a 150-Kb clone encompassing the leukocyte Ig-like receptor (LILR)B1 (ILT2), LILRB4 (ILT3), and LILRA1 (LIR6) genes) and 1060P11 (a 160-Kb clone that contains ten killer cell Ig-like receptor (KIR) genes). Both the KIR and LILR families are encoded within the leukocyte receptor complex, and are involved in immune modulation. We have also produced a novel mAb to LILRA1 to facilitate expression studies. The LILR transgenes were expressed in a similar, but not identical, pattern to that observed in humans: LILRB1 was expressed in B cells, most NK cells, and a small number of T cells; LILRB4 was expressed in a B cell subset; and LILRA1 was found on a ring of cells surrounding B cell areas on spleen sections, consistent with other data showing monocyte/macrophage expression. KIR transgenic mice showed KIR2DL2 expression on a subset of NK cells and T cells, similar to the pattern seen in humans, and expression of KIR2DL4, KIR3DS1, and KIR2DL5 by splenic NK cells. These observations indicate that linked regulatory elements within the genomic clones are sufficient to allow appropriate expression of KIRs in mice, and illustrate that the presence of the natural ligands for these receptors, in the form of human MHC class I proteins, is not necessary for the expression of the KIRs observed in these mice.

Animals↗

PubMed2003

Constitutively active protein kinase B enhances Lck and Erk activities and influences thymocyte selection and activation.

Protein kinase B (PKB), a serine threonine kinase is critically involved in cellular proliferation and survival. To characterize its role in T cell development in vivo, we have analyzed transgenic mice that express a membrane-targeted constitutively active version of PKB (myr PKB) in thymocytes and peripheral T cells. We report that myr PKB renders proliferative responses of thymocytes more sensitive to TCR signals by increased and sustained activation of Src kinase Lck and the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway. In addition, the proliferative response of myr PKB T cells is relatively independent of calcium mobilization and calcineurin activity. We also find that myr PKB enhances phosphorylation of glycogen synthase kinase 3, a negative regulator of NFAT and T cell activation, and the recruitment of the adapter protein Cbl-c. Interestingly, we demonstrate that upon TCR/CD3 stimulation of wild-type T cells PKB is translocated into lipid rafts, adding a new role for PKB in TCR-initiated signalosome formation in T cell activation. Localization of transgenic PKB in lipid rafts could contribute to the higher TCR sensitivity of myr PKB thymocytes which is reflected in an increase in positive selection toward the CD4 lineage and variable effects on negative selection depending on the model system analyzed. Thus, our observations clearly indicate a cross-talk between PKB and important signaling molecules downstream of TCR that modulate the thresholds of thymocyte selection and T cell activation.

Animals↗

PubMed2003

Transgenic mice with hematopoietic and lymphoid specific expression of Cre.

Bacteriophage P1 Cre/loxP based systems can be used to manipulate the genomes ofmice in vivo and in vitro, allowing the generation of tissue-specific conditional mutants. We have generated mouse lines expressing Cre recombinase in hematopoietic tissues using the vav regulatory elements, or in lymphoid cells using the hCD2 promoter and locus control region (LCR). The R26R-EYFP Cre reporter mouse line was used to determine the pattern of Cre expression in each line and enabled the assessment of Cre activity at a single-cell level. Analysis showed that the vav promoter elements were able to direct Cre-mediated recombination in all cells of the hematopoietic system. The hCD2 promoter and LCR on the other hand were able to drive Cre-mediated recombination only in T cells and B cells, but not in other hematopoietic cell types. Furthermore, in the appropriate tissues, deletion of the floxed target was complete in all cells, thereby excluding the possibility of variegated expression of the Cre transgene. Both of these Cre-transgenic lines will be useful in generating tissue-specific gene deletions within all the cells of hematopoietic or lymphoid tissues.

Animals↗

PubMed2002

The CD8alpha gene locus is regulated by the Ikaros family of proteins.

Ikaros family members are important regulatory factors in lymphocyte development. Here we show that Ikaros may play an important role in CD4 versus CD8 lineage commitment decisions by demonstrating: (1) that it binds to regulatory elements in the endogenous CD8alpha locus in vivo using thymocyte chromatin immunoprecipitations, (2) that Ikaros suppresses position effect variegation of transgenes driven by CD8 regulatory elements, and (3) that mice with reduced levels of Ikaros and Aiolos show an apparent increase in CD4 populations with immature phenotype, i.e., cells that failed to activate the CD8alpha gene locus. We propose that Ikaros family members function as activators of the CD8alpha gene locus and that their associated activities are critical for appropriate chromatin remodeling transitions during thymocyte differentiation and lineage commitment.

Animals↗