Finally, we analysed the observed frequencies of cytokine-producing CD4+ T cells by scoring the results as negative (responses <0.01%) versus positive and compared the 3+ CD4+ T cells statistically in the different groups of individuals. As summarized in Dorsomorphin Table 1, the highest proportion of positive responses was found among patients with active TB, followed by those patients with cured TB (at the end of anti-mycobacterial treatment). Lower proportions of 3+ CD4+ T cells positive responses were found in individuals with LTBI, whereas all of the controls were negative (data not shown). Pair-wise comparisons of the positivity

RG7420 rates for 3+ CD4+ T cells in the four groups of individuals are summarized in

Table 1: the proportion of positive responses among active TB-infected patients was significantly higher than that recorded among patients with cured TB, individuals with LTBI and control subjects. Taken together, these data suggest that 3+ CD4+ T cells simultaneously secreting IFN-γ, IL-2 and TNF-α to three antigens of M. tuberculosis, Ag85B, ESAT-6 and the 16-kDa antigen, are more frequently found in patients with current or historic TB disease compared with LTBI which are able to control M. tuberculosis replication. This study provides a detailed analysis of the frequency and quality of cytokine-producing CD4+ T cells in patients with active TB disease, cured TB and in subjects with LTBI. Importantly, we show here that the frequency of CD4+ T lymphocytes that produce multiple cytokines (IFN-γ, IL-2 Farnesyltransferase and TNF-α)

is significantly higher in subjects with active TB disease, not supporting current beliefs that such responses may be associated with protection. In contrast, CD4+ T cells that produced IL-2 and IFN-γ, or IFN-γ alone, were lower in active TB-infected patients compared with cured TB patients or individuals who controlled infection naturally (LTBI). Lending further support to our results is the observation that this pattern of distribution of cytokine-producing CD4+ T cells was consistently observed in response to three different M. tuberculosis antigens, Ag85B, ESAT-6 and 16 kDa antigen. Data from HIV and other chronic viral infections have associated CD4+ and/or CD8+ T cells that simultaneously produce the three cytokines IFN-γ, IL-2 and TNF-α, with non-disease progression and efficient control of infection 20, 22, 23. Such “multifunctional” cell profiles have subsequently also been used to define correlates of vaccine-mediated protection against Leishmania11 and M. tuberculosis12, 24, 25 in mouse models of vaccination.