Acute Lymph Node Slices Are a Functional Model System to Study Immunity Ex Vivo.
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ABSTRACT:
SUBMITTER: Belanger MC
PROVIDER: S-EPMC7887751 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Lymph nodes (LNs) are essential secondary immune organs where the adaptive immune response is generated against most infections and vaccines. We recently described the use of live ex vivo LN slices to study the dynamics of adaptive immunity. However, when working with reactive lymph nodes from vaccinated animals, the tissues frequently became dislodged from the supportive agarose matrix during slicing, leading to damage that prevented downstream analysis. Because reactive lymph nodes expand into the surrounding adipose tissue, we hypothesized that dislodging was a result of excess lipids on the collagen capsule of the LN, and that a brief wash with a mild detergent would improve LN interaction with the agarose without damaging tissue viability or function. Therefore, we tested the use of digitonin on improving slicing of vaccinated LNs. Prior to embedding, LNs were quickly dipped into a digitonin solution and washed in saline. Lipid droplets were visibly removed by this procedure. A digitonin wash step prior to slicing significantly reduced the loss of LN during slicing from 13 to 75% to 0-25%, without substantial impact on viability. Capture of fluorescent microparticles, uptake and processing of protein antigen, and cytokine secretion in response to a vaccine adjuvant, R848, were all unaffected by the detergent wash. This novel approach will enable ex vivo analysis of the generation of adaptive immune response in LNs in response to vaccinations and other immunotherapies.
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Project description:Explants of lymphoid tissue provide a rare opportunity to assess the organization of the immune system in a living, dynamic environment. Traditionally, ex vivo immunostaining is conducted in fixed tissue sections, while live tissues are analyzed using genetically engineered fluorescent reporters or adoptively transferred, pre-labelled cell populations. Here, we validated a protocol for immunostaining and imaging in live, thick slices of lymph node tissue, thus providing a spatial "map" of the lymph node while maintaining the viability and functionality of the slices. Using anti-B220/CD45R (B cell) as a prototype antibody, the procedure for immunostaining was tested for sufficient signal to noise with respect to staining time, temperature, and wash time, and the specificity was verified in comparison to isotype controls. Immunostaining signal in live tissue slices was detectable to atleast 120??m deep for both whole antibodies and F(ab')2 fragments using the staining procedure. This procedure revealed the expected changes in B cell organization in lymph nodes from immunized mice. Cell surface staining with most antibodies did not induce cytokine secretion, and cytokine secretion in response to T cell stimulation was unaffected by immunostaining. Staining with known a mitogenic antibody (anti-CD3) simultaneously labelled the cells and activated the tissue, confirming that reagents for live immunostaining must be selected judiciously. As a proof of concept, this method was used to reveal the dynamic distribution of CD69, a T cell activation marker, in lymph node slices before and after ex vivo stimulation.
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Project description:Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis, which is mainly due to late diagnosis and profound resistance to treatment. The latter is to a large extent attributed to the tumor stroma that is exceedingly prominent in PDAC and engages in complex interactions with the cancer cells. Hence, relevant preclinical models of PDAC should also include the tumor stroma. We herein describe the establishment and functional validation of an ex vivo organotypic culture of human PDAC that is based on precision-cut tissue slices from surgical specimens and reproducibly recapitulates the complex cellular and acellular composition of PDAC, including its microenvironment. The cancer cells, tumor microenvironment and interspersed remnants of nonneoplastic pancreas contained in these 350?µm thick slices maintained their structural integrity, phenotypic characteristics and functional activity when in culture for at least 4 days. In particular, tumor cell proliferation persisted and the grade of differentiation and morphological phenotype remained unaltered. Cultured tissue slices were metabolically active and responsive to rapamycin, an mTOR inhibitor. This culture system is to date the closest surrogate to the parent carcinoma and harbors great potential as a drug sensitivity testing system for the personalized treatment of PDAC.
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