CD4 and rheumatoid arthritis: The level of overexpression observed here (∼100 pg/ml in the serum of CD4-Cre RosaIL-2 mice and ∼5 pg/ml in the serum of Cd19CreRosaIL-2 mice) are in the range of those observed in mice with genetic deletion of CD25 (Sharma et al., 2007) and in line with the IL-2 overproduction observed in certain human inflammatory diseases, such as tuberculous (∼160 pg/ml; Berktas et al., 2004), rheumatoid arthritis (∼240 pg/ml; Oncul et al., 2002), celiac disease (∼60 pg/ml; Goel et al., 2020), or myelofibrosis (∼970 pg/ml; Panteli et al., 2005).