Trypanosoma (Schizotrypanum) dionisii: Effect of Various Agents on Attachment and Entry to Macrophages in vitro and on Morphogenesis

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Abstract
The attachment and entry of T. dionisii to mouse peritoneal macrophages in vitro were studied. Both occurred to a similar extent whether parasites were live or heat-killed, and whether macrophages were obtained from normal or immunized mice. Attachment occurred equally at 4.degree. and 37.degree. C, but entry only occurred at the higher temperature. Neither was affected by pretreatment of parasites with active or inactivated complement. Entry, but not attachment, was inhibited by cytochalasin B; both were inhibited by trypsin. Immune mouse plasma (if inactivated) stimulated attachment but not entry (within 24 h). It stimulated intracellular replication of T. dionisii by multiple fission and subsequent differentiation (probably within macrophages) to small extracellular trypomastigotes. No extracellular parasite and only scanty intracellular forms survived 120 h in cultures containing non-inactivated immune mouse plasma. Attachment (in the absence of antibody) occurred to non-specific receptors in the macrophage membrane and was followed by phagocytosis of the parasites rather than active penetration of the cell.