Lighting up lymph nodes (2009)

Lymph nodes are crucial parts of the human immune system. These small, bean-shaped “glands” are found throughout the body – including the neck, armpits and groin – and most of our immune responses to foreign substances (antigens) start there. 

Fluid from throughout the body flows into the lymph nodes via a network of fine tubes, carrying a wide variety of cells and molecules. White blood cells gather in lymph nodes, and more cells collect there during an infection, making lymph nodes swell – a classic medical sign of infection. 

A research team led by Maurice Wilkins Centre Director Associate Professor Rod Dunbar has been investigating a group of white blood cells called antigen-presenting cells (APCs) with a view to designing better vaccines. Their work has led to exciting new insights into how human lymph nodes work. 

“APCs are specialised white blood cells that take up foreign substances and ‘present’ fragments of them to other immune cells. White blood cells called T cells are particularly important in recognising these fragments, triggering the body’s most sophisticated immune responses,” says Dr Dunbar. “There have been plenty of studies of these APCs in mice, but surprisingly little is known about APCs in human lymph nodes.” 

Rod and his team at The University of Auckland’s School of Biological Sciences used sophisticated stains to study frozen samples of normal human lymph nodes, provided by the Ludwig Institute for Cancer Research in Heidelberg, Melbourne. Their findings were published early in 2009 in the high-profile journal Blood. 

“We discovered that most APCs in human lymph nodes fall into two classes. APCs in the first group have migrated from the tissues, after taking up foreign material. In the lymph nodes, these APCs are found only in the areas where T cells gather, suggesting they move there as soon as they arrive from the tissues. In contrast, APCs in the second group sit mainly in positions where they can take up material from the fluid flowing into the lymph nodes. Importantly, these APCs are also found in the T cell areas, suggesting they can transport foreign material from lymphatic fluid to areas where it can be examined by T cells.” 

Rod says this work immediately suggests new strategies to improve the design and delivery of vaccines for treating cancer, by targeting the second group of APCs. A similar approach might improve vaccines for infectious diseases like tuberculosis. 

The tissue staining techniques developed during this research have also led to many new studies, including collaboration with clinicians at the Auckland District Health Board to analyse the lymph nodes of patients with lymph node cancer (lymphoma).

For an update on this story in 2011 see also: Exquisite networks

Image: Magnified image of a human lymph node treated with coloured stains to show antigen presenting cells (green), T-cells (red) and the nuclei of all cells the lymph node (blue). Image courtesy of Catherine Angel, Jenni Chen and Rod Dunbar.