beta-1,3-Glucan reduces growth of Mycobacterium tuberculosis in macrophage cultures.

The effect of beta-1,3-D-glucans SSG, from Sclerotinia sclerotiorum, or soluble (sMG) or particulate (pMG) MacroGard from baker's yeast on growth of Mycobacterium tuberculosis H37Rv in cultures of peritoneal macrophages from BALB/c mice was examined. After 24 h intracellular bacteria from lysed macrophages were cultured and the number of cfu counted. SSG given with challenge, but not 24 h after, reduced the number of M. tuberculosis cfu significantly. pMG, but not sMG, given with challenge had an even stronger inhibitory effect, which was enhanced after serum opsonization of the particles. The effect of serum-treated pMG was abrogated by addition of a monoclonal antibody to CD11b. The results indicate that beta-glucans inhibit growth of M. tuberculosis in host cells in vitro, probably due to cellular stimulation and/or competitive inhibition of uptake of bacteria via CR3 (CD11b/18).