Relationship between immune response and clinical manifestations in patients with tuberculosis

Cutaneous reactivity to purified protein derivative (PPD) and antibody levels were investigated in 122 adults and 28 children with tuberculosis. IgG anti-PPD levels (measured by ELISA and reported as absorbance at 405 nm) were higher in adult patients with the disease for more than one year (0.533 +/- 0.391, N = 38 vs 0.224 +/- 0.256, N = 50 in patients with the disease for less than one year) as well as in children with disseminated tuberculosis (0.138 +/- 0.137, N = 11, vs 0.072 +/- 0.055, N = 15 in children with localized disease). The cut-off values (mean + 2SD) for healthy children and adults were 0.09 and 0.22 absorbance at 405 nm. In both adult and pediatric patients, cutaneous reactivity to PPD was inversely correlated with antibody levels. The present data provide additional evidence for the existence of an unstable spectrum of immune response in tuberculosis patients in whom changes in clinical situation are dynamic.