An age-dependent decrease in T cell responsiveness to CD28 costimulation has been described. In order to test the hypothesis that an age-related decrease in CD28 expression by CD8+ T lymphocytes might be involved, we analysed 67 healthy donors ranging in age from 15 to 69 years for their CD8+ T cell expression of CD28 and CD57. We found a statistically significant decrease of CD28 expression through ageing and a significant increase of CD57 expression, both markers being mutually exclusive. Given that cytomegalovirus (CMV) is reported to induce CD57 expression, and since the carrier status for this ubiquitous virus increases with age in the general population, it seemed essential to evaluate whether the phenotypic age-related changes described in CD8high+ cells were not influenced by the CMV carrier status of the individuals. Accordingly, we performed a multivariate analysis to assess the independent association of age and CMV carrier status with CD28 and CD57 expression in CD8high+ cells. Results showed that the progressive decrease in CD8high+ CD28+ CD57- cells was associated only with age, while the expansion of the CD8high+ CD28- CD57+ subset depended both on age and CMV, although mainly on age. We conclude that ageing is accompanied by a progressive loss of CD28 expression in CD8+ T cells and a reciprocal enhancement of CD57 expression, both facts being probably related to the repeated antigenic stimulation occurring throughout life.

The BrucellaCapt test is an immunocapture agglutination test suggested as a possible substitute for the Coombs test in the diagnosis of human brucellosis. Here it is compared with classical tests using 321 samples from 48 patients with brucellosis (6.9 ؎ 1.7 samples per patient), including 20 patients with focal disease and 8 patients with a total of 9 relapse episodes (mean follow-up, 18 months). The BrucellaCapt test was used according to the manufacturer's instructions, and we also used a variant of the BrucellaCapt test in which the microtiter plates were not coated with antibodies against total human immunoglobulin ( Human brucellosis continues to be a major health problem worldwide. Although the endemicity of this disease is limited to some areas of the Mediterranean basin and developing countries in Asia, Africa, and Latin America, sporadic cases may develop in any area where the disease is not endemic. Thus, the illness is currently included among travelers' diseases (20).The definite diagnosis of the disease is based on the isolation of Brucella spp. in blood cultures (12, 32), but under certain clinical conditions the microorganism cannot be finally recovered. In the past decade, PCR has emerged as a promising alternative method to confirm the presence of the microorganism (16, 23), although its use has not been standardized. Thus, serological tests continue to play a relevant role in the diagnosis and management of patients with brucellosis (12, 31). Most classical tests used, along with the enzyme-linked immunosorbent assay method, offer good detection of anti-lipopolysaccharide agglutinating and/or nonagglutinating antibodies. However, problems in serological diagnosis continue, mainly in chronic forms of the disease and in the course of follow-up, when the meaning of persistent titers could be difficult to interpret, especially since no definite criteria of cure have yet been established (2,12,13,18,24,25).In recent years, the new immunocapture agglutination antiBrucella (BrucellaCapt [BCAP]) test has been reported to detect agglutinating and nonagglutinating antibodies with very high sensitivity (1,5,6,8,10,15,17,18,27,29). It has been suggested as a possible substitute for the anti-human immunoglobulin (Coombs) test and, perhaps, as a better marker of disease activity (1,17,27,29). The aim of the present study was to investigate the basis and mechanisms of the high sensitivity of the BCAP test and to conduct an accurate evaluation of its performance in comparison with those of classical tests for a large group of brucellosis patients with several forms of the disease over a prolonged follow-up period. MATERIALS AND METHODSPatients and serum samples. Serum samples from 48 patients diagnosed with brucellosis at Bellvitge Hospital, a tertiary teaching hospital in Barcelona, Spain, were included. These patients were part of a series of patients with brucellosis who were treated and prospectively followed up in our hospital over a period of years, as reported elsewhere (2, 3). For all patients with po...