Although the ␤ 2 -adrenergic receptor (␤ 2 AR) is the most extensively characterized G-protein-coupled receptor (GPCR), the effects of ␤-agonists on T-cell subtype function remain poorly understood. In contrast to studies suggesting lack of ␤ 2 AR expression on type 2 T cells, we demonstrate that type 2 interleukin-13 ؉ (IL-13 ؉ ) T cells (CD4 ؉ or CD8 ؉ ) in human peripheral blood lymphocytes (PBLs) can respond directly to ␤-agonist, with

SummaryCells of monocytic lineage can initiate extravascular fibrin deposition via expression of blood coagulation mediators. This report is about experiments on three mechanisms with the potential to modulate monocyte-initiated coagulation. Monocyte procoagulant activity was examined as a function of lipid cofactor, protein cofactor, and specific inhibitor expression during short-term culture in vitro. Lipid cofactor activity was measured as the initial rate of factor X activation by intrinsic-pathway components, the assembly of which depends on this cofactor. Lipid cofactor activity levels changed by <30% during 48-h culture. Protein cofactor, i.e., tissue factor (TF) antigen was measured by enzyme immunoassay. It increased from 461 pg/ml to a maximum value of 3,550 pg/ml at 24 h and remained at 70% of this value. Spedfic TF activity, measured as factor VII-dependent factor X activation rate, decreased from 54 to 18 nM FXa/min between 24 and 48 h. TF activity did not correlate well with either lipid cofactor or TF protein levels. In contrast, the decrease in TF activity coincided in time with maximal expression of tissue factor pathway inhibitor (TFPI) mRNA, which was determined using reverse transcriptase polymerase chain reaction (RT-PCR), and with maximal TFPI protein levels measured by immunoassay. The number of mRNA copies coding for TFPI and TF in fleshly isolated blood monocytes were 46 and 20 copies/cell, respectively. These values increased to 220 and 63 copies/cell during short-term cell culture in the presence of endotoxin. Results demonstrate concomitant expression by monocytes of genes coding for both the essential protein cofactor and the specific inhibitor of the extrinsic coagulation pathway. Together with functional and antigenic analyses, they also imply that the initiation of blood dotting by extravascular monocyte/macrophages can be modulated locally by TFPI independently of plasma sources of the inhibitor.

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