Increases in helminth-induced IL-21 protein levels disappear upon sample freezing.

•Intestinal worm infections stimulate increased intestinal IL-21 production.•Differences in IL-21 levels are only observed in fresh intestinal homogenates; in frozen samples, differences can no longer be measured.•The negative effect of freezing does not impact IL-13 levels, that remain elevated in fresh and frozen samples to the same degree.