Binding of platelets to human monocytes: a source of artifacts in the study of the specificity of antileukocyte antibodies.

A serious and often ignored source of artifacts when testing the specificity of antibodies is the contamination of leukocyte preparations with platelets which subsequently adhere to monocytes. The presence of Ca2+ chelating agents or acetylsalicylic acid in the washing buffers inhibits adhesion of platelets to monocytes, thus permitting an accurate distinction among antibodies that are specific for monocytes, platelets or both. The analysis of the specificity of various new or recently described monoclonal antibodies reactive with these cell types is reported here.