Molecular features of macrophage activation.

Cellular activation is mainly defined as the response of a cell to exogenous signals eventually leading to changes in protein expression and cellular function. Originally, macrophage activation was mainly associated with phagocytic function. Later other effector functions such as cytokine secretion, upregulation of cell surface receptors came into focus. For a while macrophage activation was classified as being either pro-inflammatory or anti-inflammatory and certain signal transduction pathways were associated with these two conditions. Most recent findings on transcriptional and epigenetic level, however, suggest that the molecular features of macrophage activation are significantly more complex. Here, we will introduce a novel and integrative model of macrophage activation. Albeit recognizing that macrophage activation cannot be reduced to nuclear processes, we will focus in this review on the most recent findings concerning transcriptional and epigenetic regulation of macrophage activation. Understanding the complexity of the central regulatory mechanisms in the nucleus will form a foundation for deciphering all the different effector functions that are associated with macrophage activation.

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