Phagocytosis of Bacteroides nodosus by ovine peripheral blood leucocytes

Phagocytosis of Bacteroides nodosus by ovine peripheral blood leucocytes (PBL) was examined after organisms had been opsonized in sera from normal sheep, or from animals immune to, or infected with ovine footrot . Ingestion of bacteria, as assessed microscopically or by counting isotopically-labelled organisms spectrometrically was effected in suspensions by polymorphonuclear leucocytes (PMN). Opsonization of bacteria in immune serum, particularly its IgG2 isotype, enhanced the rate of phagocytosis by PMN compared with that promoted by normal serum or medium alone. Whereas IgG2 from immune serum also increased the rate of ingestion of B. nodosus by adherent PMN, IgM and IgG1 from immune serum also initiated phagocytosis of bacteria by adherent ovine monocytes. Leucocytes from normal, immune or infected sheep of different breeds ingested B. nodosus with equal facility.