Selective chemotaxis of Ia antigen-positive blood monocytes in response to a macrophage chemotactic lymphokine extractable from PPD-induced delayed hypersensitivity reaction site in guinea-pigs.

Intraperitoneal injection of 10 micrograms PPD into BCG-immunized guinea-pigs induced enrichment of Ia-positive macrophages in the peritoneal exudates and Ia-positive monocytes in the peripheral blood. The peritoneal fluids (PF) free of exudate cells exhibited distinct macrophage chemotactic activity (MCA). Most of the MCA were absorbed by the antibody to macrophage chemotactic factor c (MCF-c), which was isolated as a complex of macrophage chemotactic lymphokine (mol. wt. 12,500) and serum protein (as a carrier protein) from skin site of PPD-induced delayed-type hypersensitivity (DTH) reaction in guinea-pigs and highly purified. The PF and MCF-c selectively attracted Ia-positive blood monocytes rather than Ia-negative monocytes, while MCF-a and -b, which were also isolated from the same skin lesions, attracted Ia-negative monocytes but not Ia-positive monocytes, suggesting that massive Ia-positive macrophage accumulation in the exudates may be associated with the selective emigration of Ia-positive monocytes (as the precursors of macrophages) due to macrophage chemotactic lymphokine or MCF-c.