IL-7 is integral to the survival of CD8+ naïve and memory T cells, and not surprisingly several clinical trials are in progress to evaluate the therapeutic benefits of IL-7 administration in viral infections (ClinicalTrials.gov Identifier: NCT04501796), lymphopenia (ClinicalTrials.gov Identifiers: NCT05600920, NCT04781309) and cancer (ClinicalTrials.gov Identifiers: NCT05075603). This evidence concerns the gene IL7 and lymphopenia.