Guarding the Gills

What am I looking at?

This is a fluorescently labeled image of the gills and amphibranchial lymphoid tissue of a zebrafish. The gills are the feather-shaped structures at the top of the image (1). The nuclei of all the cells are purple (2). The immune cells (T cells) in the amphibranchial lymphoid tissue are gold (3). The actin filaments contained in the cells are light blue (4).

Biology in the background

Fish and other underwater organisms use gills to breathe. The gills extract oxygen from the water. However, pathogens in the water can pass over the gills and could cause infection if they’re left unchecked.

A newly characterized type of tissue has been shown to help defend the gills and surrounding tissue from infection. This amphibranchial lymphoid tissue has a high concentration of T cells, which serve several important functions in the immune system. Different types of T cells can destroy bacteria, cells infected with a pathogen, or cells that have become cancerous. Others can activate other immune cells to respond to an infection or even regulate their response to make sure it does not get out of control.

These T cells can reach 10 micrometers across, or roughly 7.5 times smaller than the width of a human hair.

Technique

This image was created using confocal microscopy.