Immunofluorescence of sperm probed against anti-MNS1. Immunofluorescence using freshly collected caput epididymal sperm (A), freshly collected cauda epididymal sperm (B), cauda epididymal sperm incubated in non-capacitating medium (C), cauda epididymal sperm incubated in capacitating medium (D), or cauda epididymal sperm incubated in medium mimicking epididymal luminal fluid (E) and probed against anti-MNS1 was performed. MNS1 localized to the sperm flagellum and post-acrosomal region. A 5 μm bar is indicated on all images. Nomarski differential interference contrast micrographs are located to the right of each fluorescent image.