Finally, individual cell lines have been derived from such outgrowths by using hCG production as a marker for selection (Harun et al. 2006) but the claim that such cells are stem cells (Harun et al. 2006; Frost et al. 2010) may be overstated in view of the fact that high hCG production is a feature of differentiated TB and a TB stem cell phenotype remains unproven. Here, CGA is linked to tuberculosis.