Analysis of transforming growth factor-beta 1 (TGF-beta1) expression in human monocytes infected with Mycobacterium avium at a single cell level by ELISPOT assay.

Transforming growth factor beta 1 (TGF-beta1) has been implicated in the pathogenesis of a number of diseases including infection with intracellular pathogens such as Mycobacterium avium complex (MAC). In this study, we developed an ELISPOT assay for measurement of active TGF-beta1 produced by peripheral blood mononuclear cells (PBMC) from healthy individuals in response to LPS or MAC. The frequency of TGF-beta1 producing cells was significantly (p<0.04) higher in response to LPS (10 microg/ml) as compared to unstimulated cells (n=4). Moreover, the frequency of TGF-beta1 producing cells was threefold higher in monocyte (MN)-enriched cell population than those in PBMC indicating that the source of TGF-beta1 producing cells in PBMC was MN. In addition, the frequency of TGF-beta1 producing cells in response to MAC (10:1, cfu:MN) was significantly higher (p<0.03) than unstimulated cells. However, the frequency of TGF-beta1 producing cells in response to MAC (10:1) was eight to ninefold lower than that by LPS (10 microg/ml). Moreover, there was a correlation between the level of total TGF-beta1 in 24-h culture supernatants and the number of TGF-beta1 producing cells upon MAC stimulation. TGF-beta1 ELISPOT-assay may be a sensitive and a powerful tool for detection of TGF-beta1 producing cells, and may be helpful in elucidation of the nature of TGF-beta1 production at sites of diseases.