AbstractIn the preceding studies, protoplast‐like “spherical bodies” were detected electron microscopically in mice which were challenged intramuscularly, approximately 15 days before, with an attenuated strain ofStreptococcus pyogenes. The “spherical bodies” were 0.5–1.5 Mm in diameter, poor in ultra‐structural preservation of the cytoplasm, devoid of cell walls, and indistinguishable from those discovered in the buffy coat of peripheral blood from patients with mucocutaneous lymph node syndrome (MCLS).The present investigation was intended to elucidate the intracellular localization of the “spherical bodies” and to understand better the mechanisms responsible for the elimination of viable streptococci from the infected sites. Accordingly, a larger amount of bacterial inoculum was injected i.m. into mice immunized, in advance, against streptococcal infection, and every biopsy specimen was obtained on day 3 postchallenge.Subsequently, ingested “spherical bodies” were detected under an electron microscope in the cytoplasm of phagocytic cells, including polymorphonuclears, eosinophils and fibroblasts, situa