PDGF AA homodimers are potent chemoattractants for fibroblasts and neutrophils, and for monocytes activated by lymphocytes or cytokines.

The A-chain homodimers of the platelet-derived growth factor (PDGF AA) are widely expressed in normal and transformed cells. The mitogenic properties of PDGF AA are well established; however, the chemotactic potential of PDGF AA remains controversial. We now show that PDGF AA is a strong chemoattractant for human monocytes, granulocytes, and fetal bovine ligament fibroblasts. However, highly purified (greater than 98%) monocytes require the addition of lymphocytes or IL-1 for chemotactic responsiveness to PDGF AA but not for full chemotactic activity with formyl-methionyl-leucyl-phenylalanine (fMLP) or C5a. These results indicate that PDGF AA is a potent chemoattractant. These results also indicate that monocytes require activation either by lymphocytes or exogenous cytokines in order to respond chemotactically to PDGF AA but not to fMLP or C5a and suggest roles of the lymphocyte and cytokine in the chemotactic response of the monocyte to PDGF AA in vivo.