Interleukin-8 secretion by peripheral blood monocytes exposed to PF4/heparin or control antibodies.

Monocytes derived from individual healthy donors (see “Materials and methods”) were incubated in duplicate with antigen in serum-free media (SFM) alone (■) or SFM containing PF4 (░), heparin (▨), or PF4 + heparin (▤). The following stimulants were coincubated in the presence of antigen for 6 hours: SFM, lipopolysaccharide (LPS; 100 ng/mL), KKO, isotype control (ISO), HITT, or control plasma. IL-8 levels were measured in cell supernatants by enzyme-linked immunosorbent assay. Data shown for HIT patient are representative of 2 patients studied. P < .05 by a 2-tailed t test for KKO versus ISO (∗) or HITT versus control (#) in the presence of PF4.