Question 6 of 6 Advanced Scenario
How would you design controls for antigen-specific T-cell stimulation?
Short answer
Include unstimulated or vehicle background, an irrelevant-antigen control, and a positive stimulus that demonstrates viable T cells can respond. Define antigen-presenting conditions, assay timing and readouts so antigen-specific responses are distinguishable from bystander activation.
Why
Start with the antigen presentation route. For short peptides, know whether the expected response requires a particular HLA context and adequate presenting cells. Match vehicle or peptide solvent concentration in the negative wells and consider an irrelevant peptide pool to measure antigen-unrelated stimulation.
Include a functional positive control such as a validated viral recall peptide pool or a non-specific polyclonal stimulus, noting that these measure different capacities. Measure live CD4 and CD8 cells, baseline and background cytokine or activation-marker expression and a defined response threshold. Run technical controls for staining, compensation and spectral overlap.
In a clinical donor panel, replicate independent donors and consider baseline immunity and HLA diversity. A rise in IFN-γ can reflect nonspecific inflammation, so supportive readouts such as CD154, CD137, proliferation or antigen-binding reagents may be valuable according to the question. Prespecify how background subtraction, QC failures and low event counts will be handled.
Common mistakes
- Calling any cytokine response antigen-specific without vehicle, irrelevant antigen and functionality controls
The interviewer might ask next
Why is a PMA-ionomycin response not by itself evidence of peptide specificity?