CD40LG and Arthritis: The present study aims to estimate the seroprevalence of brucellosis in humans attending a tertiary care hospital, King George's Medical University, Lucknow, U.P. The overall prevalence recorded in this study was 9.5% and 11.5% by anti-brucella IgM and IgG ELISA, and the study concluded that brucellosis is more frequent in explained arthritis (control) patients than unexplained arthritis (cases) patients.