Immunomodulatory properties of Mycoplasma pulmonis. I. Characterization ofthe immunomodulatory activity

For many years, it has been recognized that Mycoplasma infection affects th e host's immune system in different ways. In this work, experiments were pe rformed to characterize the influence of Mycoplasma pulmonis infection on v arious immunological parameters and to follow the kinetics of their variati ons. A Balb/c mouse model was used to assess hematological evaluations, cha nges in spleen weight, antibody responses against sheep erythrocytes, neutr ophil phagocytosis, colloidal carbon clearance, and anti-Mycoplasma antibod y responses. At the hematological level, infected animals were found to hav e significantly increased total lymphocyte and polymorphonuclear leukocyte counts and an augmentation in spleen weight. Seven days after Mycoplasma in fection, antibody responses against sheep erythrocytes were considerably di minished, and at days 7 and 14 after infection, phagocytic activity was als o reduced. After I week of infection, the colloidal carbon clearance patter n was decreased, and during the whole infectious process, anti-Mycoplasma a ntibody titers were found to be low. Results from this part of research sho w a persistent infection that does not resolve in a short period, which is associated with a general dysfunction in the immune system and poor immune responses against several different antigens. (C) 2001 Elsevier Science BN. All rights reserved.