How are antibodies involved in the protective mechanism of susceptible mice infected with T. cruzi?

Host resistance to Trypanosoma cruzi is dependent on both natural and acquired immune responses. During the acute phase of the infection the presence of IFN-gama, TNF-alpha, IL-12 and GM-CSF has been closely associated with resistance, whereas TGF-beta and IL-10 have been associated with susceptibility. Several investigators have demonstrated that antibodies are responsible for the survival of susceptible animals in the initial phase of infection and for the maintenance of low levels of parasitemia in the chronic phase. However, how this occurs is not yet understood. Our results and other data in the literature support the hypothesis that the protective role of antibodies in the acute phase of infection is dependent mostly on their ability to induce removal of bloodstream trypomastigotes from the circulation in addition to other concomitant cell-mediated events.

Participation of autonomic nervous system in the pathogenesis of Chagas disease

Evidences accumulated over the last decade give adequate proof for the existence of circulating antibodies in Chagas disease which binds to ß adrenergic and muscarinic cholinergic receptor of lymphocytes and myocardium. The interaction of the antibodies with lymphocytes and cardiac neurotransmitter receptors behaving as an agonist, triggers in the cells intracellular signal transductions that alter the physiological behaviour of this cells. These events converted the cells in pathologically active cells. Thus, antibodies activating ß adrenergic receptors of T helper (Th) lymphocytes increase cAMP and releases PGE2 by T suppressor/cytotoxic (Ts/c) cell, inducing in this way, immunosuppression by simultaneous inhibition of Th and stimulation of Ts/c cell function. All these antibodies actions were mimetized by parasite's membranes. On the other hand, the interaction of antibodies against heart ß adrenergic and cholinergic receptors trigger physiologic, morphologic, enzymatic and molecular alterations, that leading to cardiac damage. The analysis of the prevalence and distribution of these antibodies shows a strong association with seropositive asymptomatic patients with autonomic dysfunction in comparison with those asymptomatic without alteration of the heart autonomic disorders: pointing to that the presence of these antibodies may partially explain the cardiomyoneuropathy of Chagas disease, in which the sympathetic and parasympathetic systems are affected. The deoposit of autoantibodies on the myocardial neurotransmitter receptors, behaving like an agonist, could induced desensitization and/or down regulation of the receptors. This in turn, could led to a progressive blockade of myocardium neurotransmitter receptors, with sympathetic and parasympathetic dennervation, a phenomenon that has been described in the course of Chagas cardioneuropathy