Caspase-3 Is Transiently Activated without Cell Death during Early Antigen Driven Expansion of CD8+ T Cells In Vivo

Background: CD8 + T cell responses develop rapidly during infection and are swiftly reduced during contraction, wherein.90 % of primed CD8 + T cells are eliminated. The role of apoptotic mechanisms in controlling this rapid proliferation and contraction of CD8 + T cells remains unclear. Surprisingly, evidence has shown non-apoptotic activation of caspase-3 to occur during in vitro T-cell proliferation, but the relevance of these mechanisms to in vivo CD8 + T cell responses has yet to be examined. Methods and Findings: We have evaluated the activity of caspase-3, a key downstream inducer of apoptosis, throughout the entirety of a CD8 + T cell response. We utilized two infection models that differ in the intensity, onset and duration of antigen-presentation and inflammation. Expression of cleaved caspase-3 in antigen specific CD8 + T cells was coupled to the timing and strength of antigen presentation in lymphoid organs. We also observed coordinated activation of additional canonical apoptotic markers, including phosphatidylserine exposure. Limiting dilution analysis directly showed that in the presence of IL7, very little cell death occurred in both caspase-3 hi and caspase-3 low CD8 + T cells. The expression of active caspase-3 peaked before effector phenotype (CD62L low) CD8 + T cells emerged, and was undetectable in effector-phenotype cells. In addition, OVA-specific CD8 + cells remained active caspase-3 low throughout the contraction phase. Conclusions: Our results specifically implicate antigen and not inflammation in driving activation of apoptotic mechanisms without cell death in proliferating CD8 + T cells. Furthermore, the contraction of CD8 + T cell response following expansion i

Lack of Functional Selectin Ligand Interactions Compromises Long Term Tumor Protection by CD8+ T Cells

Central memory CD8+ T cells expressing the adhesion molecule CD62L (L-selectin) are potent mediators of anti-cancer immunity due to their ability to proliferate extensively upon antigen re-stimulation. The interaction of selectin with its ligands mediates leukocyte rolling along high endothelial venules. Mice deficient in α(1,3) Fucosyltransferase IV and VII (FtDKO) lack functional L, P and E selectin ligands. Thus, we addressed whether the lack of selectin ligand interactions alters tumor protection by CD8+ T cells in FtDKO mice. Listeria monocytogenes-OVA (LM-OVA) infection evoked potent OVA-specific CD8+ T cells that proliferated and contracted at similar kinetics and phenotype in FtDKO and wild-type mice. Additionally, OVA-specific CD8+ T cells in both mouse strains exhibited similar phenotypic differentiation, in vivo cytolytic activity and IFN-γ expression. However, FtDKO mice succumbed to B16-OVA tumors significantly earlier than wild-type mice. In contrast, FtDKO mice evoked strong recall memory CD8+ T cell responses and protection to systemic LM-OVA re-challenge. The diminished tumor protection in FtDKO mice was not related to defective antigen presentation by dendritic cells or reduced proliferation of antigen-specific CD8+ T cells. However, WT or FtDKO OVA-specific CD8+ T cells showed significantly reduced ability to traffic to lymph nodes upon adoptive transfer into naïve FtDKO recipients. Furthermore, FtDKO OVA-specific CD8+ T cells displayed poor ability to infiltrate tumors growing in WT mice. These results reveal that selectin ligand expression on host endothelium as well CD8+ T cells may be important for their efficient and continued extravasation into peripheral tumors

Biochemical Engineering of Surface α2–8 Polysialic Acid for Immunotargeting Tumor Cells

To target tumor cells for immunotherapy, we evaluated the feasibility of altering the epitopes on the surface polysialic acid of tumor cells. A precursor (N-propionylmannosamine), when incubated with leukemic cells, RBL-2H3 and RMA, resulted in substitution of the N-acetyl groups of surface alpha2-8 polysialic acid with N-propionyl groups. Expression of the altered alpha2-8 N-propionylpolysialic acid on the surface of tumor cells induced their susceptibility to cell death mediated by monoclonal antibody 13D9 (mAb 13D9), which specifically recognizes alpha2-8 N-propionylated polysialic acid. The expression of alpha2-8 N-propionylated polysialic acid and the lysis of tumor cells by antibody-dependent cytotoxicity depended on the time and dose of incorporation of N-propionylated mannosamine. In vivo, mAb 13D9 effectively controlled metastasis of leukemic cells RMA when mice were administered the precursor N-propionylated mannosamine

Triagem farmacologica de plantas com atividade anticonvulsivante

BV UNIFESP: Teses e dissertaçõe

Immunotherapy and fertility control by immunization against Gonadotropin-releasing hormone: Curr.Opin.Immunol.

NRC publication: Ye

The expanding universe of T-cell subsets: Th1, Th2 and more: Immunol.Today

NRC publication: Ye

Interleukin (IL) 4, in the absence of antigen stimulation, induces an anergy-like state in differentiated CD8+ TC1 cells : Loss of IL-2 synthesis and autonomous proliferation but retention of cytotoxicity and synthesis of other cytokines

NRC publication: Ye

Radioimmunoassay of gonadotropin-releasing hormone

NRC publication: Ye

Cytokine-deficient CD8 + Tc1 cells induced by IL-4: Retention of inflammation and perforin- and Fas-cytotoxicity but compromised long-term killing of tumor cells: J.Immunol.

NRC publication: Ye