Effects Of Transforming Growth Factor On Cryptococcal Infection In Mice And The Functions Of Macrophage Against Cryptococcus Neoformans

BackgroundCryptococcus neoformans is a opportunistic pathogenic fungi which predominantly infect immunocompromised individuals,such as AIDS/HIV,cancers and long-term use of immunosuppressants groups.The yeast or spores usually enter the body through the respiratory tract,resulting in primary lung infection.C.neoformans could pass through blood brain barrier and arrive in the central nervous system,leading to the deadly cryptococcal meningitis.The outcome of C.neoformans infection is highly depend on the patient’s immune state,a Th-1-dominated immune response contribute to clear the infection.Alveolar macrophage is the first immune cell that defense against C.neoformans infection.AM resists the invasion of C.neoformans through endocytosis and oxidation in the first time,and AM is also the key point that link the innate immunity and adaptive immunity.Macrophage could recruit T cells to infection site,form a cytokine microenvironment and regulate subsequent acquired immune response.Macrophage plays a significant role in defense against C.neoformans.Transforming growth factor-β(TGF-β)is pleiotropic cytokine and play an important part in regulate immune response.TGF-β could affect immune cells proliferation,differentiation as well as corresponding functions,induce immune tolerance and affect Th1/Th2 cell homeostasis.This study will explore the effects of TGF-β on phagocytosis and cytotoxicity of macrophages as well as the role of TGF-β in the resistance to C.neoformans.ObjectiveThis study aim at investigating the effects of TGF-β on macrophage function,as well as the role of TGF-β in the resistance to C.neoformans.MethodsBefore the C.neoformans infection,using recombinate mouse TGF-β interfere with J774 A.1 macrophage and then observing the changes of phagocytic index.Interfering the infected macrophage with TGF-β,then observing the changes of intracellular and extracellular fungal burden respectively and evaluating the killing ability of macrophage.To further investigate the changes of macrophage cytotoxicity,we detect the secretion of lysozyme and nitric oxide and compare the level of TGF-β intervention group with control group.Establishing a model of inhalation infection of cryptococcus in mice,and treat the mice with recombinant mouse TGF-β by tail vein injection.In the early and late stages of infection,the two groups were intervened separately.Observing the survival curve,fungal burden of lung and brain tissues,as well as the changes of Th1/Th2/Th17 cytokine concentration of lung,brain and peripheral blood.ResultsThe phagocytic index of macrophages decreased after the treatment of TGF-β,while the secretion of lysozyme and production of NO increased after the intervention.The killing ability to intracellular and extracellular both enhanced.In the inhalation infection mice,TGF-βpre-infection intervention group demonstrated a decreased ability of defense against C.neoformans and died earlier than other groups.Besides,the fungal burden of lung increased and the amount of C.neoformans that spread into brain rising in the pre-infection intervention group.The level of IFN-γ and TNF-αincreased while IL-6 concentration decreased.In addition,all the Th cytokines remained constant in the brain tissue and peripheral blood.The group treated with TGF-β in the late stage of infection demonstrates that reduced fungal burden in the lung tissue,while had no effect on fungal burden of brain.In addition,the level of Th1 cytokine TNF-αincreased,while other Th cytokines didn’t change both in the brain and peripheral blood.ConclusionsTGF-β can inhibit the phagocytosis,but TGF-β could enhance the killing ability of macrophage through increasing secretion of lysozyme and NO.In the model of inhalation infection of C.neoformans in mice,at the early stage,TGF-β intervention will inhibit the phagocytosis and subsequent limit effective inflammatory response,which leads to the decreased ability of defense against infection,dissemination of C.neoformans and earlier death.TGF-β intervention at the late stage could improve macrophage killing function,increase the level of TNF-αin lung,and then enhance the anti-cryptococcal ability,which contribute to lower the fungal burden of lung and help to limit the infection.