Baez IB, et al. - Given the stimulation of matrix metalloproteinases secretion in the host of M. tuberculosis, researchers examined sputum samples of patients with varying degrees of mycobacterial load for the activities of matrix metalloproteinase 9 (MMP-9) and 2 (MMP-2) isoforms. They collected 39 sputum samples from patients without tuberculosis and 48 sputum samples from patients with tuberculosis. Bacillary load, determined by bacilloscopy, was low in 12 and high in 36. The activity of MMP-2 and MMP-9 isoforms was determined by gelatin zymography. Results suggest no direct involvement of MMP-2 isoforms with the development of tuberculosis infection. However, MMP-9 isoforms showed variations that corresponded with the progression of tuberculosis infection. More information is needed concerning the influence of MMP-9 isoforms on the formation and progression of granuloma, and their utility as markers of progression of tuberculosis infection.