CD4 and infection: Recently, we found an expansion of the Treg population and subsequent increased in vitro immunosuppressive functions of the CD4+CD25+ cells isolated from the ceca of the Salmonella-infected chickens by day 4 post-infection that increased steadily throughout the course of the 14 days of infection, whereas the number of CD4+CD25+ cells in the non-infected controls remained steady throughout the study.