This ELISA kit provides quantitative measurement of interleukin-21 (IL-21) in human samples, supporting research into T follicular helper cell function, germinal center dynamics, and adaptive immune regulation. Because IL-21 is often present at low baseline concentrations in circulation yet rises sharply in autoimmune flares and chronic viral infections, the kit is engineered to resolve these biologically meaningful shifts across multiple sample matrices.
Detection Range: The 9.38–600 pg/mL range spans reported circulating IL-21 levels in healthy individuals (typically <50 pg/mL) through the elevated concentrations observed in systemic lupus erythematosus, rheumatoid arthritis, and chronic hepatitis B cohorts. Most serum or plasma samples can be assayed neat, though stimulated cell culture supernatants may require dilution.
Sensitivity: At 4.69 pg/mL, the kit detects IL-21 in low-abundance contexts such as unstimulated peripheral blood samples, early-stage autoimmune disease sera, and saliva, where concentrations often fall below 20 pg/mL.
Sample Compatibility: Validation across serum, plasma, saliva, and tissue homogenates enables paired systemic-versus-local analyses—for example, comparing circulating IL-21 with levels in inflamed synovial or intestinal tissue within the same study.
Assay Efficiency: A 50–100 µL sample requirement and 1–5 hour protocol accommodate limited-volume clinical specimens and time-sensitive Tfh cell polarization experiments requiring same-day readouts.
This kit is particularly suited for studies of lupus nephritis, inflammatory bowel disease, and vaccine-induced germinal center responses.