The recruitment of mononuclear cells in lungs is a key event in the pathogenesis of mycoplasma respiratory disease, but the cascade of events responsible is unknown. Studies were conducted to determine whether beta-chemokines, which are chemotactic for lymphocytes and macrophages, are produced in murine mycoplasma respiratory disease. Our results show that mRNA expression of the macrophage chemoattractant factor (MCP-I) and macrophage inflammatory peptides (MIP-1 alpha and MIP-1 beta), but not RANTES, increases in Mycoplasma pulmonis-infected mice. Also, MCP-1 concentrations were much higher in lung extracts from mycoplasma-infected mice than in uninfected mice. As beta-chemokines are chemotactic for lymphocytes and macrophages, these results suggest that MCP-1, MIP-1 alpha. and/or MIP-1 beta, but not RANTES, contribute to mononuclear cell infiltration associated with murine mycoplasma respiratory disease. Thus, the activation of cells to produce beta-chemokines is associated with mycoplasma infection, and the beta-chemokines, along with other factors and cytokines, are most likely involved in the cascade of events leading to mycoplasma inflammatory disease.