Chlamydia pneumoniae immunoreactivity in hippocampus and entorhinal Cortex. Detection of C. pneumoniaeantigen in the Alzheimer's disease hippocampus in panels A and B. Representative immunolabeling with mouse anti-C. pneumoniaemonoclonal antibody (Table 1, #5) shows immunopositivity in the dentate gyrus of the hippocampus. Immunolabeling is indicated by the magenta color and is denoted by the arrows in panel A. Extracellular and intracellular C. pneumoniaeimmunolabeling in apparent large neurons is found within the entorhinal cortex, panels C and D. Prominent labeling (magenta) denoted by the arrows in panels C and D, is easily distinguished from intraneuronal lipofuscin (golden brown) denoted by the arrowheads (panel D). High magnification images of chlamydial labeling within different cell types in the hippocampal region are illustrated in panel E (1, 8: neuroglia; 2: peri-vascular; 3, 4, 5, 6, 7, 9: neuronal). Note the apparent tangle within the neuron in E9.Size bars: A, C, and D = 50 μm; B = 20 μm; E = 10 μm.