Publications

The onset of the adaptive immune response to Mycobacterium tuberculosis is delayed compared with that of other infections or immunization, and allows the bacterial population in the lungs to expand markedly during the preimmune phase of infection. We used adoptive transfer of M. tuberculosis Ag85B-specific CD4(+) T cells to determine that the delayed adaptive response is caused by a delay in initial activation of CD4(+) T cells, which occurs earliest in the local lung-draining mediastinal lymph node. We also found that initial activation of Ag85B-specific T cells depends on production of antigen by bacteria in the lymph node, despite the presence of 100-fold more bacteria in the lungs. Although dendritic cells have been found to transport M. tuberculosis from the lungs to the local lymph node, airway administration of LPS did not accelerate transport of bacteria to the lymph node and did not accelerate activation of Ag85B-specific T cells. These results indicate that delayed initial activation of CD4(+) T cells in tuberculosis is caused by the presence of the bacteria in a compartment that cannot be mobilized from the lungs to the lymph node, where initial T cell activation occurs.

BACKGROUND

The efficacy of emergency contraceptive pills (ECPs) is currently uncertain. The best way to obtain a robust efficacy estimate would be to conduct a placebo-controlled randomized trial. We aimed to assess the feasibility of identifying women eligible for such a trial.

STUDY DESIGN

We conducted a survey of women aged 18-35 years in five sexually transmitted disease clinics and urgent care centers in Kenya and the United States in 2006.

RESULTS

Of 177 women surveyed, only 10 (6%) reported no reasons for exclusion from a potential efficacy trial. Of the rest, 149 (83%) had not recently had sex that conferred a substantial risk of pregnancy. At all sites combined, the rate of identification of potentially eligible women was 0.6 per day of interviewing.

CONCLUSION

A placebo-controlled efficacy trial of ECPs would likely require several thousand participants. Recruitment for such a trial in these types of sites would be prolonged.