Human blood and rabbit peritoneal leucocytes as sources of endogenous mediators.

"Buffy-coat" residues from human blood have been investigated as a source of leucocytic endogenous mediator (LEM). After separation from most of the erythrocytes and uptake of opsonized zymosan by the polymorphonuclear leucocytes (PML) and macrophages, the cells were incubated in Hanks' medium. To demonstrate the presence of LEM the supernatant thus produced was injected into rats and then after 24 h increases in the plasma concentrations of haptoglobin, alpha 2 macroglobulin and fibrinogen were estimated. For comparison rats were also injected with LEM prepared from rabbit peritoneal cells. Because these cells were obtained from rabbits which had been stimulated by i.p. injection of glycogen, addition of zymosan in vitro was not required. Despite the different species from which the leucocytes were obtained and the different method of preparation of LEM, similar increases in concentration of haptoglobin, fibrinogen and alpha 2 macroglobulin in the plasma of the recipient rats were obtained. Because injection of LEM resulted in very varied increases in concentration of each of the 3 plasma proteins, an attempt was made to ascertain whether positive responses for all 3 proteins occurred in the same rats or whether the rats responded randomly. The presence of endogenous pyrogen as a constituent of the LEM produced from both sources was confirmed using both rabbits and prewarmed mice (Bodel and Miller, 1976).