Inhibition of [³H]thymidine incorporation by Mycoplasma arginini‐infected cells due to enzymatic cleavage of the nucleoside

Abstract

Culture supernatants contaminated by Mycoplasma arginini inhibit the incorporation of [3H]thymidine ([3H]dThd) by cytotoxic T lymphocyte cell lines. This study presents evidence that the inhibition of uptake of the nucleoside is due to the rapid cleavage of the exogenous [3H]dThd into thymine. Uridine and cytidine as well as dThd are degraded by the mycoplasma-contaminated supernatants, while no cleavage was observed with uninfected supernatants. Cells contaminated by mycoplasma apparently release a pyrimidine-specific nucleosidase, possibly a dThd phosphorylase, which is responsible for the inhibition.

Dendritic cell maturation is induced by mycoplasma infection but not by necrotic cells

“…Since both pathways are important in DC maturation induced by other stimuli [12] it is conceivable that they may also be activated upon mycoplasma infection. These results add another example to the cell culture artifacts caused by mycoplasma [13] and to the list of organisms that can be directly recognized by DC.…”

Nucleoside-catabolizing Enzymes in Mycoplasma-infected Tumor Cell Cultures Compromise the Cytostatic Activity of the Anticancer Drug Gemcitabine

“…The cells were allowed to proliferate for 48 h and then counted using a Coulter counter. The 50% inhibitory concentration (IC 50 ) was defined as the compound concentration required to reduce cell proliferation by 50%.…”

Induction of antitumor activity in macrophages by mycoplasmas in concert with interferon

“…It was almost impossible to label mycoplasma-infected P815 cells with [3H]thymidine probably because of enzymatic cleavage of the nucleoside [13]. Thus, mycoplasma-infected P815 cells could not be used as target cells.…”

“…Until recently, cell lines maintained in in vitro cultures have often been infected with mycoplasmas in many laboratories [17,13]. Since rauch information on the antitumor defense mechanism has been obtained from in vitro experiments employing cultured tumor cells, it is important to determine whether and how mycoplasma infection of tumor cells leads to confusing results.…”