THE MEASUREMENT OF TRANSFORMING GROWTH-FACTOR TYPE-BETA (TGF-BETA) LEVELS PRODUCED BY PERIPHERAL-BLOOD MONONUCLEAR-CELLS REQUIRES THE EFFICIENT ELIMINATION OF CONTAMINATING PLATELETS

In recent years there has been an increasing interest in measuring the levels of TGF-beta produced by peripheral blood mononuclear cells (PBMC), since its abnormal regulation seems to be involved in several pathological states. Platelet-contamination, a common feature in PBMC populations isolated by the standard Ficoll-Paque method, would theoretically disturb the measurement of the levels of TGF-beta produced by mononuclear cells, since platelets represent an important source of this cytokine. In this study, supernatants of PBMC cultures from healthy subjects, either platelet-contaminated or uncontaminated, were assayed for TGF-beta activity in three different bioassays. We report that the presence of platelets led in most cases to an important overestimation of the TGF-beta levels produced by MNC in the Swiss-3T3 bioassay and in a PBMC proliferation assay. In contrast, in the Mv1Lu bioassay these levels were significantly underestimated, an effect which we attribute to the presence of other platelet-derived growth factors. These results suggest that the elimination of platelets from PBMC cultures is essential if TGF-beta production by mononuclear cells is to be studied.