Collagenase digestion down-regulates the density of CD27 on lymphocytes

Efficient enzyme-free method to assess the development and maturation of the innate and adaptive immune systems in the mouse colon

Researchers who aim to globally analyze the gastrointestinal immune system via flow cytometry have many protocol options to choose from, with specifics generally tied to gut wall layers of interest. To get a clearer idea of the approach we should use on full-thickness colon samples from mice, we first undertook a systematic comparison of three tissue dissociation techniques: two based on enzymatic cocktails and the other one based on manual crushing. Using flow cytometry panels of general markers of lymphoid and myeloid cells, we found that the presence of cell-surface markers and relative cell population frequencies were more stable with the mechanical method. Both enzymatic approaches were associated with a marked decrease of several cell-surface markers. Using mechanical dissociation, we then developed two minimally overlapping panels, consisting of a total of 26 antibodies, for serial profiling of lymphoid and myeloid lineages from the mouse colon in greater detail. Here, we highlight how we accurately delineate these populations by manual gating, as well as the reproducibility of our panels on mouse spleen and whole blood. As a proof-of-principle of the usefulness of our general approach, we also report segment- and life stage-specific patterns of immune cell profiles in the colon. Overall, our data indicate that mechanical dissociation is more suitable and efficient than enzymatic methods for recovering immune cells from all colon layers at once. Additionally, our panels will provide researchers with a relatively simple tool for detailed immune cell profiling in the murine gastrointestinal tract, regardless of life stage or experimental conditions.

The Prognostic Potential of Human Prostate Cancer-Associated Macrophage Subtypes as Revealed by Single-Cell Transcriptomics

Macrophages in the tumor microenvironment are causally linked with prostate cancer development and progression, yet little is known about their composition in neoplastic human tissue. By performing single cell transcriptomic analysis of human prostate cancer resident macrophages, three distinct populations were identified in the diseased prostate. Unexpectedly, no differences were observed between macrophages isolated from the tumorous and nontumorous portions of the prostatectomy specimens. Markers associated with canonical M1 and M2 macrophage phenotypes were identifiable, however these were not the main factors defining unique subtypes. The genes selectively associated with each macrophage cluster were used to develop a gene signature which was highly associated with both recurrence-free and metastasis-free survival. These results highlight the relevance of tissue-specific macrophage subtypes in the tumor microenvironment for prostate cancer progression and demonstrates the utility of profiling single-cell transcriptomics in human tumor samples as a strategy to design gene classifiers for patient prognostication. IMPLICATIONS: The specific macrophage subtypes present in a diseased human prostate have prognostic value, suggesting that the relative proportions of these populations are related to patient outcome. Understanding the relative contributions of these subtypes will not only inform patient prognostication, but will enable personalized immunotherapeutic strategies to increase beneficial populations or reduce detrimental populations.

A. R. ENS, Mat Lazim N, Mohamud R, Yean CY, Shueb RH. Technical Considerations in Ex Vivo Human Regulatory T Cell Migration and Suppression Assays

Regulatory T cells (Tregs) are renowned for maintaining homeostasis and self-tolerance through their ability to suppress immune responses. For over two decades, Tregs have been the subject of intensive research. The immunosuppressive and migratory potentials of Tregs have been exploited, especially in the areas of cancer, autoimmunity and vaccine development, and many assay protocols have since been developed. However, variations in assay conditions in different studies, as well as covert experimental factors, pose a great challenge to the reproducibility of results. Here, we focus on human Tregs derived from clinical samples and highlighted caveats that should be heeded when conducting Tregs suppression and migration assays. We particularly delineated how factors such as sample processing, choice of reagents and equipment, optimization and other experimental conditions could introduce bias into the assay, and we subsequently proffer recommendations to enhance reliability and reproducibility of results. It is hoped that prioritizing these factors will reduce the tendencies of generating false and misleading results, and thus, help improve our understanding and interpretation of Tregs functional studies.

Optimization of processing female genital tissue samples for lymphocyte analysis by flow cytometry

PROBLEM

A variety of methods have been used to process cervical cytobrush and genital tissue for flow cytometric evaluation of immune cell populations. We sought to optimize genital tract specimen processing and to determine if blood could be used as a model for assessment of tissue processing methods.

METHOD OF STUDY

Cervical cytobrushes, PBMCs, and genital tissue samples (cervical and endometrial biopsies) were subjected to varying processing conditions to characterize the effects on cell yields, lymphocyte viability, and surface receptors. We exposed PBMC and tissue specimens to varied collagenase types, concentrations, and exposure durations and cytobrushes to immediate vs delayed processing with/without vortexing.

RESULTS

PBMCs and tissues exposed to varying enzymatic digestion conditions demonstrated stability of some cell surface receptors, including CD3⁺ , CD4⁺ , and CD8⁺ , while others, including CCR6⁺ , were cleaved when exposed to any concentration of collagenase B, or ≥0.25 mg/mL of collagenase D. We observed increased CD69 expression (marker of cell activation) after exposure to collagenase B. Neither a 2-hour delay in cytobrush processing nor vortexing at a setting of 50% for 30 seconds had significant impacts on viability or quantities of genital immune cells of interest.

CONCLUSION

Although tissue digestion with collagenase D was sufficient to recover and analyze cells from endometrial biopsy specimens, cervical biopsy specimens required a limited exposure to collagenase B at 1 mg/mL to optimize cell yield and viability for cytometric analysis. PBMCs can be used as a model to assess the impact of tissue processing on co-receptor expression and to optimize methods prior to study implementation.

Ovalbumin induces natural killer cells to secrete Th2 cytokines IL‑5 and IL‑13 in a mouse model of asthma

Asthma is a chronic lung disease characterized by an imbalance of T-helper (Th)1/Th2 cells and their cytokine profiles. Natural killer (NK) cells constitute a considerable subset of the lymphocyte population in the lungs, and provide protection against respiratory infection by fungi, bacteria and viruses. However, the mechanism by which NK cells are involved in asthma remains to be fully elucidated. The present study analyzed the dynamic changes of NK cells and their subsets during the development of the ovalbumin (OVA)-induced allergic airway response. Lung tissues were histologically examined for cell infiltration and mucus hypersecretion. The number, activity and cytokine-secreting ability of NK cells was determined by flow cytometry. The results showed that the percentage of NK cells in the lung was decreased following OVA sensitization and challenge. However, NK cells exhibited enhanced activity and secreted more Th2 cytokines (IL-5 and IL-13) following OVA challenge. Furthermore, the proportion of CD11b⁻ NK subsets increased with the development of asthma, and CD11b⁻ CD27⁻ NK cells were the primary NK subset producing Th2 cytokines. These findings suggest that, although NK cells are not the crucial type of lymphocytes involved in asthma, OVA induces NK cells to secrete Th2 cytokines that may be involved in the pathogenesis of asthma.

Robust method for isolation of tumor infiltrating lymphocytes with a high vital cell yield from small samples of renal cell carcinomas by a new collagenase-free mechanical procedure

BACKGROUND

Tumor-infiltrating lymphocytes (TIL) play an important role in the pathogenesis of renal cell carcinoma. Characterization of TIL requires efficient isolation procedures, especially in early stage disease when the tumor is of small in size. Conventional methods for isolating TIL are based on enzymatic tissue digestion, most frequently with collagenase. Collagenase isolation is limited by poor cell recovery, altered expression of cell-surface molecules, and impaired TIL-functionality. To overcome these limitations, we developed and optimized conditions for a robust collagenase-free mechanical procedure for improved isolation of TIL from renal cell carcinoma samples.

METHODS

TIL from tumor samples and T cells from peripheral blood were collected from 12 patients undergoing partial or radical nephrectomy. Samples were subjected to an enzymatic reference protocol and to a newly established mechanical isolation protocol. After viability staining, TIL-subpopulations were quantified and phenotyped by immunohistochemistry and flow-cytometric analysis, and were compared to characteristics of peripheral blood T cells. As a marker for TIL-functionality, T-cell cytokine induction was quantified after polyclonal stimulation.

RESULTS

We show that this new technique is rapid and allows identification of CD4 and CD8 T-cell subpopulations including CD4, CD8, and regulatory T cells expressing anergy markers such as programmed death-1 (PD-1) or B- and T-lymphocyte attenuator. When compared to the reference protocol involving collagenase digestion, the yield of TIL after mechanical isolation was higher and the expression of cell-surface markers was better preserved. Moreover, although antitumor activity was not assessed, mechanically isolated TIL are at least equally functional as T cells from peripheral blood, as polyclonal stimulation induced cytokines such as interferon-γ and tumor necrosis factor-α in both TIL and T cells from peripheral blood.

CONCLUSION

The mechanical procedure may be applied as a robust and rapid alternative to collagenase digestion for isolation of high amounts of phenotypically and functionally intact TIL from fresh tumor samples.

Improved protocol for simultaneous analysis of leukocyte subsets and epithelial cells from murine and human lung

PURPOSE

To study and isolate lung cells by flow cytometry, enzymatic digestion and generation of single cell suspensions is required. This significantly influences expression of cellular epitopes and protocols need to be adapted for the best isolation and subsequent analysis of specific cellular subsets.

MATERIALS AND METHODS

We optimized protocols for the simultaneous isolation and characterization of specific human and murine lung cell types. For alveolar epithelial cells (AEC), a primarily dispase based digestion method and for leukocytes, a primarily collagenase based technique was adapted. Protocols were applied in parallel in either single experimental mice or human lung specimens.

RESULTS

Optimized dispase/DNase digestion yielded a high percentage of Epcam+CD45-CD31- AEC as assessed by flow cytometry. Epcam+CD45-CD3-CD11b-CD11c-CD16/32-CD19-CD31-F4/80- AEC were readily sortable with high purity and typical morphology and function upon in vitro stimulation with lipopolysaccharide or respiratory-syncytial-virus (RSV) infection. To analyze lung leukocytes, specimens were digested with an adapted collagenase/DNase protocol yielding high percentages of viable leukocytes with typical morphology, function, and preserved subset specific leukocyte markers. Both protocols could be applied simultaneously in a single experimental mouse post mortem. Application of both digestion methods in primary human lung specimens yielded similar results with high proportions of Epcam+CD45- human AEC after dispase/DNase digestion and preservation of human T cell epitopes after collagenase/DNase digestion.

CONCLUSION

The here described protocols were optimized for the simple and efficient isolation of murine and human lung cells. In contrast to previously described techniques, they permit simultaneous in-depth characterization of pulmonary epithelial cells and leukocyte subsets such as T helper, cytotoxic T, and B cells from one sample. As such, they may help to comprehensively and sustainably characterize murine and human lung specimens and facilitate studies on the role of lung immune cells in different respiratory pathologies.

Reliable and High Efficiency Extraction of Kidney Immune Cells

Immune system activation occurs in multiple kidney diseases and pathophysiological processes. The immune system consists of both adaptive and innate components and multiple cell types. Sometimes, the cell type of interest is present in very low numbers among the large numbers of total cells isolated from the kidney. Hence, reliable and efficient isolation of kidney mononuclear cell populations is important in order to study the immunological problems associated with kidney diseases. Traditionally, tissue isolation of kidney mononuclear cells have been performed via enzymatic digestions using different varieties and strengths of collagenases/DNAses yielding varying numbers of viable immune cells. Recently, with the development of the mechanical tissue disruptors for single cell isolation, the collagenase digestion step is avoided and replaced by a simple mechanical disruption of the kidneys after extraction from the mouse. Herein, we demonstrate a simple yet efficient method for the isolation of kidney mononuclear cells for every day immune cell extractions. We further demonstrate an example of subset analysis of immune cells in the kidney. Importantly, this technique can be adapted to other soft and non-fibrous tissues such as the liver and brain.

HMGB1 blockade differentially impacts pulmonary inflammation and defense responses in poly(I:C)/LPS-exposed heart transplant mice

A large number of recipients are in a compromised immune defense condition because of the routine application of immunosuppressive regimens after heart transplantation. Our previous work demonstrated that blockade of high-mobility group box 1 (HMGB1) prolongs the graft survival. Whether and how HMGB1 blockade impacts respiratory responses against pathogen-like challenge in organ transplant recipients when it improves cardiac graft are not elucidated. At the present study, after abdominal heterotopic heart transplantation, the recipient mice were treated with HMGB1 mAb, and then challenged with poly(I:C) or LPS intratracheally on day 7 post transplantation. We found that the level of bronchoalveolar lavage (BAL) HMGB1 was elevated after heart transplantation, and aggravated responses to respiratory tract poly(I:C)/LPS challenge were observed. HMGB1 neutralizing mAb treatment in poly(I:C)-challenged recipient mice alleviated pulmonary histopathological changes, neutrophil infiltration and inflammatory cytokine release, but unaffected the level of IFN-β, the distribution of CD11b(+)CD27(+)/CD11b(+)CD27(-) NK cell subsets, and CD8(+) T cell responses. In LPS-exposed recipient mice, HMGB1 mAb treatment ameliorated pulmonary inflammatory damage and enhanced the phagocytosis of phagocytic cells. Thus, this study may establish a basis for the application of HMGB1 blockade to improve the outcomes of heart transplant recipients because HMGB1 inhibition ameliorates pulmonary inflammation, but maintains defense-associated responses.

Reduced expression of CD27 by collagenase treatment: implications for interpreting b cell data in tissues

Surface markers have been used to identify distinct cell subpopulations and to delineate various stages of maturation or activation of lymphocytes. In particular CD27 is used for delineation of naïve and memory B cell populations, and is readily detected by flow cytometry. We here used flow cytometry to examine the expression of CD27 on lymphocytes isolated from various tissues of rhesus macaques, and found its expression was consistently low to absent on intestinal cell suspensions. However, immunohistochemistry revealed abundant CD27+ cells in intestinal tissue sections. Further investigation showed the marked loss of CD27 expression on processed intestinal cells was due to collagenase digestion of intestinal tissues, yet CD27 expression was recoverable within hours of cell isolation. By combining confocal microscopy, we confirmed that only a fraction of B cells express CD27, in contrast to expression on all T cells from tissues examined including the gut. Taken together, our results suggest that CD27 may be a memory marker for B cells, but not for T cells, since essentially all CD3 T cells expressed CD27. In summary, it is important to consider the influence of isolation procedures on cell surface expression of phenotypic markers, especially when examining tissue-resident lymphocytes by flow cytometry.