Monitoring Antigen Processing for MHC Presentation via Macroautophagy.

Macroautophagy has recently emerged as an important catabolic process involved not only in innate immunity but also in adaptive immunity. Initially described to deliver intracellular antigens to MHC class II loading compartments, its molecular machinery has now also been described to impact the delivery of extracellular antigens to MHC class II loading compartments through the noncanonical use of the macroautophagy machinery during LC3-associated phagocytosis (LAP). Therefore, in pathological situations (viral or bacterial infections, tumorigenesis) the pathway might be involved in shaping CD4+ T cell responses.In this chapter we describe three basic experiments for the monitoring and manipulation of macroautophagic antigen processing toward MHC class II presentation through the canonical pathway. Firstly, we will discuss how to monitor autophagic flux and autophagosome fusion with MHC class II loading compartments. Secondly, we will show how to target proteins to autophagosomes in order to monitor macroautophagy dependent antigen processing via their enhanced presentation on MHC class II molecules to CD4+ T cells. And finally, we will describe how macroautophagy can be silenced in antigen presenting cells, like human monocyte-derived dendritic cells (DCs).

Measurement of Dipeptidylpeptidase Activity in vitro and in vivo.

Dipeptidylpeptidases (DPPs) are serine proteases, which cleave small proteins and peptides possessing a proline or an alanine in the second position of their N-terminus. Among the members of this family, dipeptidylpeptidase 4 (DPP4) is constitutively expressed in the extracellular space. DPP4 is found at the surface of many hematopoietic and non-hematopoietic cells and is also present in many biological fluids in a bioactive soluble form. DPP4 expression is modulated by inflammation, and measurements of its activity have been used as biomarker for disease. Here, we describe a method to evaluate the enzymatic activity of DPP4 in vitro and in vivo.

Mouse CD8+ T Cell Migration in vitro and CXCR3 Internalization Assays.

Chemokines are molecules that regulate the positioning of cells during homeostasis and inflammation. CXCL10 is an interferon-induced chemokine that attracts cells that express the chemokine receptor CXCR3 on their surface. CXCL10 expression is often induced upon inflammation and guides lymphocytes, such as T and NK cells, into the injured tissues. Notably, CXCL10 binding to CXCR3 induces receptor internalization and, therefore, low CXCR3 levels in cells positive for CXCR3 expression can be indicative of chemokine signaling. Here, we describe an in vitro method to evaluate the ability of murine CD8+ T cells to migrate towards recombinant murine CXCL10; and a flow cytometry assay to measure CXCR3 expression levels at the surface of T cells, after exposure to different doses of chemokine.

Comment on "NRF2 activation by antioxidant antidiabetic agents accelerates tumor metastasis".

Experimental cancer models must consider the role of the immune system.

Antigen processing for MHC presentation via macroautophagy.

Macroautophagy has recently emerged as an important catabolic process involved not only in innate immunity but also in adaptive immunity. Initially described to deliver intracellular antigens to MHC class II loading compartments, its molecular machinery has now also been described to enhance the delivery of extracellular antigens to MHC class II loading compartments by accelerating phagosome maturation. Therefore in pathological situations (viral or bacterial infections, tumorigenesis) the pathway might be involved in shaping CD4(+) T cell responses.In this chapter we describe three basic experiments for the monitoring and manipulation of macroautophagic antigen processing towards MHC class II presentation. Firstly, we will discuss how to monitor autophagic flux and autophagosome fusion with MHC class II loading compartments. Secondly, we will show how to target proteins to autophagosomes in order to monitor macroautophagy-dependent antigen processing via their enhanced presentation on MHC class II molecules to CD4(+) T cells. And finally, we will describe how macroautophagy can be silenced in antigen presenting cells, like human monocyte-derived dendritic cells (DCs).

Impaired IFN-γ production and proliferation of NK cells in multiple sclerosis.

NK cells are multicompetent lymphocytes of the innate immune system with a central role in host defense and immune regulation. Studies in experimental animal models of multiple sclerosis (MS) provided evidence for both pathologic and protective effects of NK cells. Humans harbor two functionally distinct NK-cell subsets exerting either predominantly cytotoxic (CD56(dim)CD16(+)) or immunoregulatory (CD56(bright)CD16(-)) functions. We analyzed these two subsets and their functions in the peripheral blood of untreated patients with relapsing-remitting MS compared with healthy blood donors. While ex vivo frequencies of CD56(bright)CD16(-) and CD56(dim)CD16(+) NK cells were similar in patients and controls, we found that cytokine-driven in vitro accumulation and IFN-γ production of CD56(bright)CD16(-) NK cells but not of their CD56(dim)CD16(+) counterparts were substantially diminished in MS. Impaired expansion of CD56(bright)CD16(-) NK cells was cell intrinsic because the observed effects could be reproduced with purified NK cells in an independent cohort of patients and controls. In contrast, cytolytic NK-cell activity toward the human erythromyeloblastoid leukemia cell line K562, the allogeneic CD4(+) T cell line CEM and allogeneic primary CD4(+) T-cell blasts was unchanged. Thus, characteristic functions of CD56(bright)CD16(-) NK cells, namely cytokine-induced NK cell expansion and IFN-γ production, are compromised in the NK cell compartment of MS patients.