To determine the time-course of IL-10 production during B. abortus infection, C57BL/6 mice were infected intraperitoneally (IP) with 5×105 CFU of the virulent B. abortus strain 2308 and IL-10 production was determined at 3, 9, 15, and 21 days post-infection (d.p.i.). This evidence concerns the gene IL10 and infection.