Here, we present a protocol to induce colonic inflammation in mice by adoptive transfer of syngeneic CD4+CD45RBhigh T cells into T and B cell deficient recipients. Clinical and histopathological features mimic human inflammatory bowel diseases. This method allows the study of the initiation of colonic inflammation and progression of disease.
There are many different animal models available for studying the pathogenesis of human inflammatory bowel diseases (IBD), each with its own advantages and disadvantages. We describe here an experimental colitis model that is initiated by adoptive transfer of syngeneic splenic CD4+CD45RBhigh T cells into T and B cell deficient recipient mice. The CD4+CD45RBhigh T cell population that largely consists of naïve effector cells is capable of inducing chronic intestinal inflammation, closely resembling key aspects of human IBD. This method can be manipulated to study aspects of disease onset and progression. Additionally it can be used to study the function of innate, adaptive, and regulatory immune cell populations, and the role of environmental exposures, i.e., the microbiota, in intestinal inflammation. In this article we illustrate the methodology for inducing colitis with a step-by-step protocol. This includes a video demonstration of key technical aspects required to successfully develop this murine model of experimental colitis for research purposes.
The inflammatory bowel diseases (IBD) Crohn’s disease and ulcerative colitis result from an incompletely defined and complex interaction between host immune responses, genetic susceptibility, environmental factors, and the enteric luminal contents1. Recent genome-wide association studies report associations between immune cell regulatory genes and IBD susceptibility2,3. Both innate and adaptive immune cell intrinsic genes are represented in these studies, indicating a central role for these cell populations in IBD pathogenesis.
There currently exist more than 50 animal models of human IBD. While no one model perfectly phenocopies human IBD, many are useful for studying various aspects of human disease, including disease onset and progression and the wound-healing response. In the method described here, intestinal inflammation is initiated with syngeneic splenic CD4+CD45RBhigh T cell adoptive transfer into T and B cell deficient recipient mice4. The CD4+CD45RBhigh T cell population contains mainly naïve T cells primed for activation that are capable of inducing chronic small bowel and colonic inflammation. This method allows the researcher to modify key experimental variables, including both innate and adaptive immune cell populations, to answer biologically relevant questions relating to disease pathogenesis. Additionally, this method provides precise initiation of disease onset and a well-characterized experimental time course. This permits the kinetic study of clinical features of disease progression in mice. Intestinal inflammation induced by this method shares many features with human IBD, including chronic large and small bowel transmural inflammation, pathogenesis driven by cytokines such as TNF and IL-12, and systemic symptoms such as wasting5. Thus, it is an ideal model system for studying the pathogenesis of human IBD.
The method here describes in detail the protocol for inducing experimental colitis by adoptive transfer of CD4+CD45RBhigh T cells into Rag1-/- mice. We discuss key technical steps, expected results, optimization, and trouble-shooting. We address the required elements for the successful development of this murine model of intestinal inflammation for research purposes.
NOTE: Ensure that all animal protocols are approved by and in compliance with Institutional Animal Care and Use Committee (IACUC) regulations and the National Research Council’s Guide for the Care and Use of Laboratory Animals. Donor mice may be either male or female, but recipient mice should be male. If female recipients are to be used, the donor mice must be female5. Maintain colonies using regular, non-sterile bedding and non-acidified water, as these may impact the intestinal microbiota, and, thus, the colitis phenotype of the mice5,6.
1. Experimental Preparation
2. Isolation of Splenic T cells
3. Enrichment of CD4+ T cells
NOTE: Follow manufacturer’s instructions for specific products used in this section.
4. Labeling and Sorting Cells7
Figure 1: Representative flow cytometry plots of CD4+CD45RB T cell populations during FACS analysis. (A–C) FITC CD4- and PE CD45RB-stained splenocytes from donor C57BL/6 mice were sorted by FACS into CD4+CD45RBhigh and CD4+CD45RBlow T cell populations. (A) Doublet events were excluded on the forward scatter plot. (B) Lymphocytes were gated in the forward and side scatter plot. (C) CD4+ T cells were gated, and (D) CD4+CD45RB+ T cells were plotted on a PE versus Events histogram. CD4+CD45RBlow cells were considered to be the lowest 20% of CD45RB+ cells. CD4+CD45RBhigh cells were defined as the highest 40% of CD45RB+ cells.
5. Injection of Cells into Recipients
6. Monitoring of Disease Progression in Recipient Animals
Figure 2: Clinical and gross pathological signs of inflammation occur after transfer of wild type CD4+CD45RBhigh T cells into Rag1-/- and NRDKO recipient mice11. (A) NRDKO recipients lost on average 10% of their initial body weights by 5 weeks post-transfer, whereas Rag1-/- recipients did not exhibit clinical signs of disease at this time. Each point represents the mean percentage of initial body weight for the cohort ± SEM. **, p <0.005. (B) Some mice developed severe intestinal inflammation, as demonstrated by the presence of rectal prolapse. This is a representative picture of rectal prolapse in a NRDKO recipient mouse. (C) Grossly, colons from both Rag1-/- and NRDKO recipient mice are thickened and shortened compared to colons from Rag1-/- and NRDKO mice without T cell adoptive transfer. Colons from NRDKO recipient mice show severe inflammation and increased colon weights (data not shown). Please click here to view a larger version of this figure.
Approximately 10 x 106 CD4+CD45RBhigh T cells from 10 spleens from adult C57BL/6 donor mice are reliably isolated. This number will vary depending on the age and strain of the donor mouse and the proficiency of the researcher. When 4 x 105 C57BL/6 CD4+CD45RBhigh T cells are transferred into C57BL/6 Rag1-/- recipient mice, clinical signs of disease emerge around week 5 post-repletion or sooner if mice are genetically susceptible to more severe disease (Figure 2, 3)11,12. CD3+ T cells are seen accumulating in colons of Rag1-/- recipients as early as 3 weeks (Figure 3A)12.
Figure 3: Transfer of wild type CD4+CD45RBhigh T cells into Rag1-/- and RKO/δKD recipients induces chronic intestinal inflammation12. (A) (Original magnification 10X, H&E and CD3 immunohistochemistry). H&E staining (top panels) illustrates epithelial hyperplasia, inflammatory cell infiltrates, and crypt abscesses (arrow) present in RKO/δKD recipients but not Rag1-/- recipients. Colons from RKO/δKD recipient mice demonstrated marked accumulation of CD3+ T cells by CD3 IHC (bottom panels) compared to colons from Rag1-/- recipients. (B) Colons from RKO/δKD recipient mice demonstrated more severe inflammation as compared to colons from Rag1-/- recipient mice as determined by histology scoring. (C, D) Colonic explant cultures from RKO/δKD recipient mice secreted less IL-10 (C) and more IL-12p40 (D) than did colonic explant cultures from Rag1-/- recipient mice. Please click here to view a larger version of this figure.
We previously published that adoptive T cell transfer into Nfil3-/- / Rag1-/- double knockout recipients (NRDKO) develop more severe colitis compared to Rag1-/- recipient mice (Figure 2)11. NFIL3 negatively regulates IL-12p40 in murine colonic macrophages independently of its IL-10-inducing effects13. Dysregulation of IL-12p40 and IL-10 is implicated in the pathogenesis of human IBD1. Thus, unchecked IL-12p40 production in adoptive transfer NDRKO recipient mice results in more rapid disease progression, as shown by weight loss (Figure 2A). Some NRDKO recipient mice developed severe disease resulting in rectal prolapse (Figure 2B). Grossly, colons from NRDKO recipient mice are thickened and shortened, representing a large influx of inflammatory cells into the colon, compared to Rag1-/- recipient mice (Figure 2C).
Comparatively, in Rag1-/- mice with a nonfunctional PI3K catalytic subunit p110δ in non-lymphocyte populations (RKO/δKD), CD4+CD45RBhigh T cell repletion induces a similarly rapid and severe clinical course of disease compared with NRDKO mice (Figure 3)12. Histological analysis at 3 weeks demonstrates colonic tissue hypertrophy, inflammatory cell infiltrates, and crypt abscesses (arrow) in RKO/δKD recipients compared to Rag1-/- recipients (Figure 3A). Recipient mice in this experiment were euthanized at 3 weeks due to a significant number that had lost 20% of their initial body weight. Histological scores, as determined by a pathologist blinded to the experimental groups and based on specific criteria developed in our lab12, were higher in RKO/δKD recipient mice compared to Rag1-/- recipient mice (Figure 3B). Additionally, spontaneous cytokine production from colonic explant cultures demonstrated decreased IL-10 and enhanced IL-12p40 production by RKO/δKD recipient mice compared to Rag1-/- recipient mice (Figure 3C, D)12. Again, increased IL-12p40 and decreased IL-10 production is implicated in the pathogenesis of human IBD1.
Here we describe a step-by-step protocol inducing colonic inflammation in mice by adoptive transfer of CD4+CD45RB+ T cells into immunodeficient mice. We used C57BL/6 donor spleens and syngeneic Rag1-/- recipient mice, although other strains (e.g., BALB/c, 129S6/SvEv, non-obese diabetic (NOD)) and genetic models of immunodeficiency (e.g., SCID, Rag2-/-) may also be used4,14-16. It is well established that background strain affects experimental colitis severity in mice1. Furthermore, the enteric microbiota in a murine population varies widely between facilities, even between those within the same institution6,17. While Figures 2 and 3 do not show the development of colitis in Rag1-/- mice at 4 weeks post-transfer, in our and others’ experiences Rag1-/- recipients develop clinical disease between 6 and 9 weeks after transfer of CD4+CD45RBhigh T cells18-23. This variability in clinical course and disease expression and should be taken into account when establishing this model of experimental colitis to minimize intra- and inter-experimental inconsistency.
A critical step for the reproducibility of this experiment is FACS isolation of pure populations of CD4+CD45RBhigh cells without residual activated/memory/regulatory T cells. This involves a proficient understanding of flow cytometry. It is important to first negatively select non-viable and CD4- cells. Then, using a simple histogram for CD45RB-PE cells, select the highest 40% of cells to represent the CD45RBhigh T cells and the lowest 20% as the CD45RBlow T cells. Other markers to consider using for isolation of naïve CD4+ T cells are CD62L and CD25, although in our experience CD45RBhigh and CD45RBlow separation is sufficient and reproducible5. Additionally, it is possible to vary the ratio of CD45RBhigh to CD45RBlow T cells transferred into recipients to study the effects of regulatory T cell populations on disease phenotype. Work with someone who is familiar with flow cytometry initially to set up the FACS protocol and then using that protocol in future experiments. Additionally, a step where significant variation may impact results in this protocol is the intraperitoneal injection of T cells into recipient mice. Here, the intra- and inter-experimenter variability can greatly impact the outcome of the experiment. It is suggested that the person performing this step is comfortable with handling mice and with the injection technique so as to minimize variability in quality and quantity of cells adoptively transferred. Additionally, it is important to change needles between mice, as needle dulling can affect the efficacy of the intraperitoneal injection.
Steps of the protocol that require optimization include Section 3: Enrichment of CD4+ T cells and Section 4: Labeling and Sorting Cells. Optimization of the CD4+ T cell enrichment depends on the magnetic system used and should follow the manufacturers’ instructions. Options for magnetic cell separation systems are listed in the Table of Specific Reagents/Equipment. It is advisable to enrich for CD4+ T cells by negative selection, as directly labeling this population can affect the phenotype of the cells. There are many antibody clones available for labeling cells for FACS. The antibody concentration (step 4.4) should be optimized to ensure specific staining and to obtain an adequate separation of CD4+CD45RB T cell populations during FACS.
Development of this protocol may require trouble-shooting. First, the success of each experiment depends on the proficiency of the researcher and will increase with improved skill in these methods. However, consistently obtaining low numbers of T cells for adoptive transfer may be caused by not keeping cells on ice during isolation, resuspending centrifuged cells too aggressively, or the use of splenocytes from young mice with small spleens. Additionally, optimize the concentration of anti-CD4 and anti-CD45RB labeling antibodies for staining to avoid deficient or non-specific cell staining (see above). If recipients develop widely varying degrees of intestinal inflammation, the most likely cause is imprecise intraperitoneal injection technique. This should improve with practice and can be monitored by immunohistologic staining of CD3+ cells in the intestines of recipient mice. Additional things to consider include the gender of donor and recipient mice and normal variations in disease penetration. When male recipient mice are used, either male or female donor mice are appropriate. However, if female recipient mice are to be used, the donor mice must be female5. In our and others’ experiences, penetration of disease in this model is 85-90%5. Thus it is expected that some mice may not develop intestinal inflammation, given other causes of marked variability in disease severity have been ruled out. Keep in mind there is marked variability in phenotypes between facilities within an organization and outside it with regard to murine gastrointestinal microbiota and practices that influence the microbiota6,17. Thus, the robustness of phenotype or kinetics of disease in Rag1-/- recipient mice may vary widely based on one’s location. Therefore, it is important to determine the best parameters for these experiments based on the timeline and results obtained from each individual facility.
Here we describe the methodology of the well-characterized adaptive transfer murine model of chronic small bowel and colonic inflammation that resembles human IBD5. This step-by-step protocol illustrates key techniques for the successful development of this method for research purposes. This is a particularly useful animal model of human IBD, as it allows for synchronization of disease and manipulation of various cell populations. However, the immunodeficient recipient mice are genetically modified to develop without mature adaptive immune cells, which likely affect downstream disease outcomes. Despite this, the method described here will be very useful in future studies determining the impact of the enteric microbiota, innate immune cells, and adaptive immune regulatory cells in the pathogenesis of human IBD.
The authors have nothing to disclose.
This work was supported by American Gastroenterological Association (AGA) Research Scholars Award and Crohn’s and Colitis Foundation of America (CCFA) Career Development Award (to S.Z.S.), NIH NIDDK F30 DK089692 (to E.C.S.), and University of North Carolina Center for Gastrointestinal Biology and Disease Grant P30 DK34987 (Histology Core). The UNC Flow Cytometry Core Facility is supported in part by an NCI Center Core Support Grant (P30CA016086) to the UNC Lineberger Comprehensive Cancer Center. We thank Luke B. Borst from North Carolina State University College of Veterinary Medicine for his help with histopathological analysis and immunohistochemistry.
Name of Reagent/ Equipment | Company | Catalog Number | Comments/Description |
10x PBS | Gibco | 14200075 | |
12x75mm round-bottom tube | Falcon | 352052 | |
15 ml conical | Corning | 430790 | |
26g x 3/8 Needle | BD Biosciences | 305110 | |
50 ml conical | Corning | 430828 | |
70 um Cell Strainer | Fisherbrand | 22363548 | |
BD IMagnet | BD Biosciences | 552311 | |
β-mercaptoethanol | Thermo Scientific | 35602 | |
CD4-FITC IgG2b | eBioscience | 11-0041 | |
CD45RB-PE IgG2a | BD Pharminogen | 553101 | |
Complete Media | RPMI-1640, 1% Pen/Strep, 10% FBS, 0.0004% β-ME | ||
FACS tube + strainer | BD Falcon | 352235 | |
Glass Microscope Slides | Fisherbrand | 12550A3 | |
Heat-inactivated FBS | Gemini | 100-106 | |
Labeling Buffer | 1x PBS, 0.5% BSA, 2 mM EDTA | ||
Lysis Buffer | 0.08% NH4Cl, 0.1% KHCO3, 1 mM EDTA | ||
MoFlo XDP | Beckman Coulter | ||
Mouse CD4 T lymphocyte Enrichment Set – DM | BD Biosciences | 558131 | |
Mouse IgG2a-PE | BD Pharminogen | 553457 | |
Mouse IgG2b-FITC | eBioscience | 11-4732 | |
Pasteur pipet | Fisherbrand | 13-678-20D | |
Penicillin-Streptomycin Solution, 100X | Corning Cellgro | 30-002-CI | |
Petri Dish | Fisherbrand | 875713 | |
Pure Ethanol 200 Proof | Decon Labs | 2705-HC | |
RPMI-1640 | Gibco | 11-875-093 | |
Syringe | BD Biosciences | 309597 | |
Trypan blue | Corning Cellgro | 25-900-CI | |
Wash Media | RPMI-1640, 1% Pen/Strep, 0.0004% β-ME |