Age-related increase in resistance to acute Trypanosoma cruzi infection in rats is associated with an appropriate antibody response.

Inoculation at weaning with Trypanosoma cruzi in inbred "l" rats resulted in a self-resolving acute infection characterized by marked parasitaemias, whereas challenge to adult rats revealed a mild disease with extremely low parasitaemias. To explore the mechanisms underlying such age-associated differences in disease outcome, we analysed the in vitro replication of T. cruzi, nitric oxide and tumour necrosis factor-alpha (TNF-alpha) production in peritoneal macrophages (PMs), the serum concentrations of the specific immunoglobulins (Igs) IgM and IgG, antibodies exhibiting lytic activity against bloodstream forms of T. cruzi and circulating levels of nitrate, TNF-alpha and interferon-gamma (IFN-gamma). Macrophages from young rats were as effective as their adult counterparts for restraining intracellular parasite replication. When stimulated with IFN-gamma, culture supernatants from young PMs contained higher amounts of nitrite and TNF-alpha. Serum samples from 4 and 7 days post infection revealed easily detectable amounts of nitrate, with values being further augmented by day 7 post infection and significantly higher in the young group. TNF-alpha levels were only detected in the young group by day 7 post infection. Both groups had increased amounts of IFN-gamma in their sera, although in adult rats, this trend was followed by a significant drop at day 7, with young rats showing values still higher by the same time point evaluation. In contrast, young rats presented significantly lower levels of IgM and IgG antibodies during the first week of infection. Increased resistance in adult rats seems to be the result of a more appropriate antibody production.

Low occurrence of arthritic manifestations in patients with pulmonary tuberculosis. T cell subsets and humoral studies.

Given the suspected role of mycobacteria in the establishment of disorders with an autoimmune background and joint damage, a study was conducted to analyze whether rheumatic symptoms were likely to be present in tuberculosis (TB) patients. To this end, 330 patients with a bacteriologic confirmation of tuberculosis were investigated for the presence of arthritic complaints. The latter were recorded in five of them with rheumatic symptoms mostly involving interphalangeal and metacarpophalangeal joints, and preceding the clinical manifestations of the TB illness. Three out of these five patients remained arthritic by the time of the bacteriologic conversion and fulfilled the criteria for the diagnosis of rheumatoid arthritis. In the two remaining patients sputum negativization was accompanied by a disappearance of rheumatic manifestations. These patients were also assessed for their peripheral levels of major T cell subsets as well as for the presence of autoantibodies. Comparisons with a series of non-arthritic TB cases, rheumatoid arthritis patients, and controls revealed that presence of rheumatic manifestations was associated with a different profile of autoantibody formation and T cell subset changes. Evidence recorded in the present study indicates that joint affectation in TB is a rare event, being rather the exception than the rule.