After immunization, large numbers of B lymphocytes that are specific for the foreign compound form an aggregate of dividing cells known as a germinal center, seen here in a widefield fluorescence micrograph made by Associate Research Scientist Ann M. Haberman, Ph.D., in the laboratory of Mark J. Shlomchik, M.D., Ph.D., professor of laboratory medicine and immunobiology. As the germinal center expands, non-responding B cells (green) are displaced by responding B cells (blue), forming a corona around the germinal center. Contact with the fine extensions of follicular dendritic cells (red) encourages long-term survival and differentiation of germinal center B cells.

Confocal micrograph of a tick from the family Ixodes, the vector for Lyme disease. Ruth R. Montgomery, Ph.D., senior research scientist in the Department of Internal Medicine’s Section of Rheumatology, and Utpal Pal, Ph.D., now an assistant professor at the Virginia-Maryland Regional College of Veterinary Medicine, imaged living ticks 24 hours after injecting them with fluorescent dyes to label surface structures and cells in the midgut.

Scanning electron micrograph by Daniel Biemesderfer, Ph.D., assistant professor of medicine, of a glomerulus in the kidney of the two-toed amphiuma (Amphiuma means), a salamander found in the southeastern United States. Glomeruli are found in the nephron, the basic structural and functional unit of all vertebrate kidneys. They are composed of capillaries and an epithelium that filters the blood. Here, epithelial cells (round and oval structures) are seen sending out extensions to surround the capillaries (tubular structures) beneath.

A section of rectal mucosa tissue from a macaque monkey stained with fluorescent antibodies to DC-SIGN (green) and CCR5 (red) and imaged with confocal microscopy by Akiko Iwasaki, Ph.D., associate professor of immunobiology. DC-sign binds to the human immunodeficiency virus (HIV-1) and CCR5 is a co-receptor for HIV-1. Cell nuclei are seen in blue.