1Department of Pediatrics, Emory University, 2Department of Pathology & Laboratory Medicine, Emory University
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Geem, D., Medina-Contreras, O., Kim, W., Huang, C. S., Denning, T. L. Isolation and Characterization of Dendritic Cells and Macrophages from the Mouse Intestine. J. Vis. Exp. (63), e4040, doi:10.3791/4040 (2012).
Within the intestine reside unique populations of innate and adaptive immune cells that are involved in promoting tolerance towards commensal flora and food antigens while concomitantly remaining poised to mount inflammatory responses toward invasive pathogens1,2. Antigen presenting cells, particularly DCs and macrophages, play critical roles in maintaining intestinal immune homeostasis via their ability to sense and appropriately respond to the microbiota3-14. Efficient isolation of intestinal DCs and macrophages is a critical step in characterizing the phenotype and function of these cells. While many effective methods of isolating intestinal immune cells, including DCs and macrophages, have been described6,10,15-24, many rely upon long digestions times that may negatively influence cell surface antigen expression, cell viability, and/or cell yield. Here, we detail a methodology for the rapid isolation of large numbers of viable, intestinal DCs and macrophages. Phenotypic characterization of intestinal DCs and macrophages is carried out by directly staining isolated intestinal cells with specific fluorescence-labeled monoclonal antibodies for multi-color flow cytometric analysis. Furthermore, highly pure DC and macrophage populations are isolated for functional studies utilizing CD11c and CD11b magnetic-activated cell sorting beads followed by cell sorting.
1. Dissection and Dissociation of Intestinal Epithelial Cells
Preparation of reagents and equipment:
Note: Steps 1.1 to 1.7 must be performed as quickly as possible to minimize the extent of cell death and to achieve maximum cell yield.
2. Tissue Digestion and Isolation of Intestinal Cells
Preparations of reagents and equipment:
3. Antibody Staining for Multi-Color Flow Cytometric Analysis of DCs and Macrophages
Preparations of reagents and equipment:
4. Enrichment of DCs and Macrophages from the Intestine
Preparations of reagents and equipment:
5. Gating Strategy for LP APCs
Note: Please note that unstained intestinal cells may be utilized as a negative control to assist in the proper placement of the gates to separate positive and negative populations.
6. Representative Results
Figure 1. Gating strategy for intestinal DCs and macrophages. Dead cells (A) and doublets (B and C) were first excluded from the analysis and then small intestinal cells were gated accordingly to forward and side scatter (D), and APCs were defined as CD45+I-Ab+(E). Macrophages and DCs were identified by the expression of CD11b and CD11c (F). CD103 and F4/80 expression for cells pre-gated on R1 (G), R2 (H) and R3 (I) populations was analyzed.
Figure 2. Cell yield and antibody staining quality depends on digestion time. CD11b and CD11c staining pattern and total cell yield of under- (A, D), optimally- (B, E) or over-digested (C, F) intestinal tissue.
Intestinal cells were isolated from a C57BL/6 mouse small intestine and DCs and macrophages were analyzed by FACS on the BD LSR II. Voltage and compensation were set using unstained and single fluorochrome-stained splenocytes. Dead cells (Fig. 1A) and doublets (Fig. 1B and C) were first excluded from the analysis. Cells of interest were then analyzed according to forward and side scatter (Fig. 1D) followed by gating on CD45+ and I-Ab+ cells (Fig. 1E). Thereafter, CD11b and CD11c expression was assessed among the CD45+I-Ab+ cells to delineate three regions (R1, R2, and R3; Fig. 1F). CD103 and F4/80 expression in the three regions was evaluated to distinguish between DCs and macrophages, respectively. The CD11c+ CD11bdull/- cells of R1 expressed high levels of the αE integrin, CD103, and low levels of F4/80 (Fig. 1G). CD11b+CD11c+ cells of R2 were composed of both DCs and macrophages based on their dichotomous expression of CD103 and F4/80 (Fig. 1H) while CD11b+CD11cdull/- cells of R3 constitute macrophages based on the phenotypic profile of F4/80+ and CD103- (Fig. 1I)16. Macrophages within the R2 gate and macrophages in the R3 gate have similar forward and side scatter properties and are distinguishable by CD11c expression. The functional dichotomy of these subsets remains incompletely understood.
The relationship between the duration of tissue digestion on total cell yield and the expression of CD11b and CD11c is illustrated in Figure 2. Intestinal tissue that was digested for 3 min (under-digestion) yielded low total cell number (Fig. 2D) and thus few DCs and macrophages available for characterization (Fig. 2A). Tissue digestion for 11 min produced a robust yield of live cells (Fig. 2E) with populations of DCs and macrophages that expressed high levels of CD11b and CD11c and were phenotypically distinct (Fig. 2C). In contrast, digestion for 50 min (over-digestion) resulted in a similar cell yield when compared to optimized digestion (Fig. 2E and F), however, delineation of different cell populations using CD11b and CD11c became more obscure as the expression of CD11c diminished (Fig. 2C) and the number of dead cells increased (data not shown).
Figure 3. Factors important for the optimization of cell yield and surface antigen expression. Cell yield and surface antigen expression are directly affected by the duration of tissue digestion, the specific characteristics of the collagenase, the degree of tissue mincing, and the presence or absence of inflammation, which may affect tissue integrity and cellularity. Prolonged tissue digestion may result in decreased cell viability and surface antigen expression while inadequate tissue digestion may result in a paucity of cells for analysis.
Here, we detailed a methodology for the rapid isolation of mouse intestinal DCs and macrophages for phenotypic characterization using multi-color flow cytometry and for enrichment using MACS beads and cell sorting to conduct functional studies on purified cells. Optimizing the concentration of collagenase and the duration of tissue digestion is necessary to produce a robust cell yield without compromising viability and surface antigen expression. Under-digestion yields a low total cell number and a paucity of DCs and macrophages for characterization (Fig. 2A and D). On the other hand, over-digestion yields a total cell number similar to optimized conditions (Fig. 2F) but the number of dead cells are appreciably increased (data not shown) and the quality of the staining is compromised. Similar to under-digestion, the over-digestion of tissue would complicate phenotypic characterization and purification.
Several additional parameters for consideration using this protocol are the manufacturer, type and specific lot of collagenase, the integrity and cellularity of the intestine, and degree of tissue mincing. As variability in collagenase activity may exist between different manufacturers, types of collagenase, and production lots, the potency of digestion may vary greatly and requires optimization. Hence, selection of the most appropriate type of collagenase is critical when designing an experiment as the quality and reproducibility of the data may be affected. In our experience, collagenase type VIII obtained from Sigma-Aldrich has provided the best results, however, we have also had success using collagenase type IV from Sigma-Aldrich.
While the above detailed protocol has been optimized for use on healthy small and large intestines, it can be successfully used for the isolation of DCs and macrophages from inflamed tissue exhibiting increased cellularity and architectural distortion associated with inflammation. The presence of intestinal inflammation may dramatically affect the rate of digestion—often increasing the sensitivity of the intestinal tissue to the action of proteolytic enzymes based on our experience. Therefore, the duration of digestion or the concentration of collagenase must be adapted accordingly to changes in tissue integrity associated with inflammation.
Furthermore, the degree of mincing the tissue will affect the duration of tissue digestion. Mincing the tissue into smaller pieces increases the surface area for digestion and yields more cells but precautions should be taken, as the tissue may be more susceptible to over-digestion. Consequently, the duration of digestion may need to be decreased. In contrast, poor mincing will result in larger pieces of tissue that will digest poorly resulting in a low total cell yield. Increasing the duration of digestion may compensate for poor mincing to a certain extent.
Upon optimizing the parameters for intestinal tissue digestion with collagenase, a robust cell yield can be rapidly achieved. As a result, intestinal DC and macrophage populations can be more accurately characterized and purified for functional studies to assess cytokine production, antigen presentation, and the regulation of immune cells.
No conflicts of interest declared.
We thank Aaron Rae (Emory University Department of Pediatrics and Children's Healthcare of Atlanta Flow Core) for cell sorting. This work was supported by NIH grant AA01787001, a Career Development Award from the Crohn's and Colitis Foundation of America, and an Emory-Egleston Children's Research Center seed grant to T.L.D.
|1X PBS, Ca2+- and Mg2+-free|
|Hank’s balanced salt solution (HBSS) with phenol red||Fisher Scientific||SH3001603|
|1M HEPES in 0.85% NaCl||Lonza Inc.||17-737E|
|Fetal bovine serum (FBS)||Atlanta Biologicals||S11150H||Heat-inactivated|
|0.5M EDTA (pH 8.0)||Cellgro||46-034-CI|
|Collagenase type VIII||Sigma-Aldrich||C2139|
|DNase I||Roche Group||14785000||Stock solution: 100mg/ml|
|LIVE/DEAD Fixable Aqua Dead Cell Stain Kit for 405 nm excitation||Invitrogen||L34957||Use at 1:1000|
|CD45-PerCP mAb (30F11)||BD Biosciences||557235||Use at 1:100|
|CD103-PE mAb (M290)||BD Biosciences||557495||Use at 1:100|
|FcγRIII/II mAb (2.4G2)||BD Biosciences||553141||Use at 1:200|
|CD11c-APC mAb (N418)||eBioscience||17-0114-82||Use at 1:100|
|MHC-II (I-Ab)-Alexa Fluor 700 mAb||eBioscience||56-5321-82||Use at 1:100|
|CD11b-eFluor 450 mAb (M1/70)||eBioscience||48-0112-82||Use at 1:200|
|F4/80-PE-Cy7 mAb (BM8)||eBioscience||25-4801-82|
|CD11b microbeads||Miltenyi Biotec||130-049-601|
|CD11c microbeads||Miltenyi Biotec||130-052-001|
|50 mL conical tubes||BD Biosciences||352098|
|Single mesh wire strainer||Chefmate|
|Small weigh boat||Fisher Scientific||08-732-116|
|100 μm cell strainer||BD Biosciences||352360|
|40 μm cell strainer||BD Biosciences||352340|
|5 mL polystyrene round-bottom tubes||BD Biosciences||352235||Use at 1:100|
|MaxQ 4450 benchtop orbital shaker||Thermo Fisher Scientific, Inc.|
|LS MACS column||Miltenyi Biotec||130-042-401|
|LSR II||BD Biosciences|
|FACSAria II||BD Biosciences|