Assay Systems for Measurement of Chemotactic Activity

The traditional view of the polymorphonuclear leukocyte (PMN) or neutrophil has been a cell whose primary function was to ingest and kill bacteria. It is becoming increasingly clear that a number of these granule constituents that were originally studied because of their antibiotic activity may in fact have other important roles in various aspects of inflammation (
1
). Accumulating evidence would support the concept that the PMN is a pivotal effecter cell in the immune response, capable of generating cytokines, chemokines, and a variety of mediators that orchestrate the process of inflammation (
2
). Of the antibacterial proteins present within the human PMN, cationic antimicrobial protein of
Mr37 kDa (CAP37) and the defensins have been shown to have chemotactic activity for monocytes (
3
,
4
). CAP37 is chemotactic at concentrations of 1.3 � 10
−8
to
−10
M for human monocytes. It appears to have no effect on neutrophil migration. In addition to confirming the chemotactic activity of CAP37 for monocytes, Flodgaard et al. (
5
) have demonstrated that CAP37 has chemotactic activity for fibroblasts and effects maturation of monocytes into macrophages. Henson et al. (
6
) have shown that instillation of CAP37 into rabbit airways leads to a significant and selective migration of rabbit blood monocytes into the lung. The minimal neutrophil and lymphocyte migration into the lung that occurred in response to CAP37 was indistinguishable from that induced by the instillation of vehicle alone.