Tregs are potent suppressors of the immune system. There is a lack of unique surface markers to define them, hence, definitions of Tregs are primarily functional. Here we describe an optimized in vitro assay capable of identifying immune imbalance in subjects at risk to develop T1D.
Regulatory T cells (Tregs) are critical mediators of immune tolerance to self-antigens. In addition, they are crucial regulators of the immune response following an infection. Despite efforts to identify unique surface marker on Tregs, the only unique feature is their ability to suppress the proliferation and function of effector T cells. While it is clear that only in vitro assays can be used in assessing human Treg function, this becomes problematic when assessing the results from cross-sectional studies where healthy cells and cells isolated from subjects with autoimmune diseases (like Type 1 Diabetes-T1D) need to be compared. There is a great variability among laboratories in the number and type of responder T cells, nature and strength of stimulation, Treg:responder ratios and the number and type of antigen-presenting cells (APC) used in human in vitro suppression assays. This variability makes comparison between studies measuring Treg function difficult. The Treg field needs a standardized suppression assay that will work well with both healthy subjects and those with autoimmune diseases. We have developed an in vitro suppression assay that shows very little intra-assay variability in the stimulation of T cells isolated from healthy volunteers compared to subjects with underlying autoimmune destruction of pancreatic β-cells. The main goal of this piece is to describe an in vitro human suppression assay that allows comparison between different subject groups. Additionally, this assay has the potential to delineate a small loss in nTreg function and anticipate further loss in the future, thus identifying subjects who could benefit from preventive immunomodulatory therapy1. Below, we provide thorough description of the steps involved in this procedure. We hope to contribute to the standardization of the in vitro suppression assay used to measure Treg function. In addition, we offer this assay as a tool to recognize an early state of immune imbalance and a potential functional biomarker for T1D.
As the only unique feature to Tregs, suppressive function should be tested reliably and uniformly between subjects at different phases of disease development within the same and between different studies. We offer details of the suppression assay developed in our laboratory as our contribution to the standardization of this assay. In our extensive optimization study, we have determined that T cell stimulation with anti-human CD3-coated beads (UCHT1 clone, in concentration of 1μg/ml (as opposed to commercially availabl…
The authors have nothing to disclose.
This study was supported by Max McGee National Research Center for Juvenile Diabetesat Medical College of Wisconsin and Children’s Research Institute of Wisconsin. The funders had no role in study design, data collection and analysis, or preparation of the manuscript.
Name of the reagent or instrument | Company | Catalogue number | Comments (optional) |
---|---|---|---|
Ficoll-Paque PLUS | Amersham Pharmacia Biotech | 17-1440-03 | |
DPBS-1X | Gibco | 14190-144 | |
Trypan Blue | Invitrogen | 15250-061 | |
anti-CD4 microbeads | Miltenyi | 130-045-101 | |
Pre-separation filters | Miltenyi | 130-041-407 | |
LS column | Miltenyi | 130-042-401 | |
EDTA | Invitrogen | 15575-020 | |
BSA | Sigma-Aldrich | B4287 | |
Anti-human CD4-APCCy7 (clone RPA-T4) | BD Pharmingen | 557852 | |
Anti-human CD25-PE (clone M-A251; IL-2Rα) | BD Pharmingen | 555432 | |
Anti-human CD8-FITC (clone RPA-T8) | BD Pharmingen | 555366 | |
Anti-human CD14-FITC (clone M5E2; LPS receptor) | BD Pharmingen | 555397 | |
Anti-human CD32-FITC (clone FLI8.26; FcγR-type II) | BD Pharmingen | 555448 | |
Anti-human CD116-FITC (clone M5D12; GM-CSFRα chain) | BD Pharmingen | 554532 | |
Dynalbeads M-450 tosylactivated | Invitrogen | 140-13 | |
Anti-human CD3 | Ancell | 144-024 | |
Buffer1 | Homemade | 0.1M Na2B4O7 pH7.6 | |
Buffer2 | Homemade | PBS/2mM EDTA/ 0.1% BSA pH7.4 | |
Buffer3 | Homemade | 0.2M Tris/0.1% BSA pH8.5 | |
Complete RPMI media | Homemade | RPMI 1640 media 2 mM L-glutamine 5 mM HEPES 100 U/μg/ml peni/strept 0.5 mM sodium pyruvate | |
[3H] thymidine | Perkin Elmer | NET027Z005MC | |
human pooled AB serum | Atlanta Biologicals | S40110 | |
Multiscreen harvest plate | Millipore | MAHFC1H60 | |
Microscint 20 | Perkin Elmer | 6013621 |