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English: Spotted fever group rickettsia–endothelial cell interaction. 1, Attachment of rickettsia via adhesins (e.g., outer membrane protein B) tohost cell receptors (e.g., Ku70); 2, recruitment of more Ku70 receptors and their ubiquitination by ubiquitin ligase; 3, signal transduction leading toactin rearrangement and engulfment; 4, rickettsia in cytoplasmic endosome; 5, rickettsial enzymes (phospholipase D and tlyC) lyse vacuolar membrane, allowing rickettsial escape into the cytosol; 6, replication by binary fission fueled by host cell building blocks; 7, rickettsial RickA activation of Arp2/3 leads to host actin-based mobility, with entry into a filopodium and extracellular release; and 8, cell-to-cell spread, or invagination into the endothelial cell nucleus (N) followed by entry into the nucleoplasm. Illustrated by Aaron Medina-Sanchez. (Walker, D. H. (2007). Rickettsiae and rickettsial infections: the current state of knowledge. Clinical Infectious Diseases, 45(Supplement 1), S39-S44.)