An independent-samples t-test showed an increased frequency of CD4+ T cells expressing IFN-γ (p = 0.034) and a significantly decreased frequency of CD4+ T cells expressing IL-2 (p = 0.037) - both ESAT-6 specific - in patients with pulmonary TB when compared to diseases other then TB (Figure 2). Here, CD4 is linked to pulmonary tuberculosis.