*5.1. Search Strategy, Study Selection, and Data Extraction*

The literature analysis was carried out on the PubMed database where the search for available articles was performed based on the following keywords: "Foxp3", "IPEX", "IPEX like", "Immunodysregulation, Polyendocrinopathy, and Enteropathy, X-Linked", "CVID", "Common Variable Immunodeficiency", and "Primary Immunodeficiency". The time range of the searched articles was established for the years 2000 to 2021 and filters related to the type of articles (clinical trials, review, systematic review) were used. Repetitions were rejected from the found articles. The suitability for the inclusion of each work into the publication was thoroughly assessed. Eventually, 223 articles were included in the review.
