Evaluation of T and B lymphocyte function in clinical practice using a flow cytometry based proliferation assay

• We present a flow cytometry based proliferation assay for clinical use
• A suitable assay for diagnostic evaluation of immunocompromised patients
• FASCIA permits to study in vitro effects of immunosuppressive drugs

The golden standard for functional evaluation of immunodeficiencies is the incorporation of [3H]-thymidine in a proliferation assay stimulated with mitogens. Recently developed whole blood proliferation assays have the advantage of parallel lymphocyte lineage analysis and in addition provide a non-radioactive alternative. Here we evaluate the Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) in a comparison with [3H]-thymidine incorporation in four patients with severe combined immunodeficiency. The threshold for the minimum number of lymphocytes required for reliable responses in FASCIA is determined together with reference values from 100 healthy donors when stimulated with mitogens as well as antigen specific stimuli. Finally, responses against PWM and SEA + SEB stimuli are conducted with clinically relevant immunomodulatory compounds. We conclude that FASCIA is a rapid, stable and sensitive functional whole blood assay that requires small amounts of whole blood that can be used for reliable assessment of lymphocyte reactivity in patients.