sentences:  They discovered that the "smooth" type of "Mycobacterium vaccae" has a substance on the outside of its cell wall which interferes with the production of Th-1 cytokines, responsible for some kinds of T-helper cell immune response.The team also found that the spleen cells of mice inoculated with "rough" "Mycobacterium vaccae" produced more Th-1 cytokines than those inoculated with "smooth" "Mycobacterium vaccae".The researchers say this may explain why different vaccines made from "Mycobacterium vaccae" vary in their effectiveness in increasing immune response to other organisms during clinical trials.