Phagocytosis of Mycoplasma salivarium by human polymorphonuclear leukocytes and monocytes

Abstract

Mycoplasmacidal activity was exhibited by human peripheral blood leukocytes in the absence of detectable specific antiserum. After incubation of varying concentrations of Mycoplasma salivarium with leukocytes changes in colony forming units (CFU) of this species per milliliter occurred. The most noticeable decrease in CFU per milliliter was that the incubation mixtures contained 5 mycoplasmas per leukocyte. At this ratio, the mycoplasmacidal activity resulted in a fivefold decrease in numbers of viable mycoplasmas afer 90 min of incubation. Continued incubation demonstrated a tenfold decrease in CFU per milliliter by 4 h. Electron micrographs of incubated mixtures of human leukocytes and M. salivarium showed this mycoplasma to be phagocytized by monocytes and neutrophils whenever mutual contact or pseudopodial formation occurred. The process was continuous. Numerous phagocytic vacuoles developed which contained multiple ingested microorganisms. After the cytoplasmic granules of the leukocytes fused with the phagocytic vacuole, the phagocytized mycoplasmas became disrupted and unrecognizable.