Background: People with Idiopathic CD4 lymphopenia (ICL) have lower numbers of a type of white blood cell called CD4 cells. White blood cells fight against infections. Low levels of CD4 cells may make a person more likely to get sick. There are no approved treatments for ICL. Researchers think a drug called belimumab may be able to help in specific situations.

Summary: This is a 52 week, single center, randomized, double-blind, placebo-controlled study. After patients maintain a stable dose of Mycophenolate Mofetil (MMF) for at least 1 month, they will be randomized to treatment with either Belimumab \& Rituximab or placebo.Patients in both groups will be on background MMF for the entirety of the study. Belimumab will be administered subcutaneously and Rituximab...

Summary: The purpose of the OBSErve-LN study is to assess the real-world use and effectiveness of belimumab in routine practice for the treatment of adults with active LN in multiple countries of interest. This study aims to provide the first long-term (up to 5 years) assessment of renal function preservation in belimumab treated participants.