12/19/2017 12:45 EST | Updated 12/19/2017 12:51 EST

Unlocking Our Immune System's 'Memory' Can Lead To Better Vaccines

The results of a new study reveal the fascinating way your body deals with an infection and prepares itself for any future attacks.

One of the easiest ways to find out if you're sick with a cold, throat infection or a chronic illness such as mononucleosis is to check for swollen lymph nodes. Just take the fingers and press gently on the neck and throat area in search of pea-sized lumps. If you happen to find them, there's a good chance you are fighting some kind of microbial attack.

Lymph nodes are part of a much larger biological network inside each of us known as the lymphatic system. It has a vital importance in keeping us healthy as its primary job is to remove unwanted chemicals such as toxins and waste products. Yet, when an infection takes hold, a different call to action takes place and the nodes become a hub for infection fighting action.

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When an invader hits, the lymph nodes become the primary staging area to prepare for an effective battle. Several different types of immune cells gather here to learn and share more about the opponent. Those that have visited the area arrive with molecular information of the attacker. They share their information with other cells including the ones responsible for the front line fighting, known as killer T-cells. The primed soldiers venture out to the battlefield where they aim to kill the intruders while others in the node ensure new recruits are properly readied for combat.

Since the lymph nodes require far more space to accommodate all the cells, they tend to enlarge. These areas remain this way until the battle has been won, making it easy for you to check their progress. Once victory has been achieved, the area quickly drains and eventually returns back to normal size within a few days.

For the most part, researchers have focused on the process involved during enlargement of the lymph nodes as this plays an important role in keeping us healthy. The process of returning the node back to its original size — known as contraction — has been given relatively less attention. For the most part, the fluid drains, the unneeded cells die and the system returns to normal.

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A T cell, left. The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi or bacteria.

But in 2014, a group of American researchers discovered a rather interesting phenomenon occurring as the lymph nodes contract. Somehow, the immune system also developed a memory of the battle and shared it with killer T-cells in preparation for another attack. This information suggested a new role for the lymph node after the infection was completed.

At the time, team was able to identify the cells performing this function as lymphatic endothelial cells, or LECs. These cells were known to be involved in maintaining the integrity of the lymph node during swelling and contraction. Yet how they managed to retain the information as well as share it with killer T-cells soldiers remained a mystery.

Now the team has come up with an answer. They have revealed how LECs manage to maintain memory and also pass the information on to the troops during this time of node contraction. The results demonstrate the lymph node is far more than a central hub for fighting infection. It also happens to be the place where memory is both stored and shared across the body.

The results of this study reveal the fascinating way your body deals with an infection and prepares itself for any future attacks.

The group took a closer look at the LECs to find out how they might be sharing memory within the lymph node. Much as they found in 2015, these cells kept molecular records of the fight in the form of antigens. However, none of this information was going directly to the killer T-cells. This meant some other cell was briefing the troops.

The team explored the different cell types in the node and eventually realized the answer lied in a rather obvious option. It's known as a migratory dendritic cell, or MDC. It's usual role is to bring antigens from the battlefield to the lymph node so the troops can be primed for battle. Yet in this case, the cells acquired the information locally so they could act as a liaison between the LECs and the killer T-cells.

With this result in place, the team tried to find out why memory seemed to occur during contraction of the lymph node. The answer turned out to be relatively straightforward. As the lymph node shrank, many of the LECs died off as they were no longer needed. The antigens contained in their cells were released into the environment and picked up by the MDCs. The information was processed in these cells and eventually given to the killer T-cells who would then retain the memory as they shipped out to other areas of the body.

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The results of this study reveal the fascinating way your body deals with an infection and prepares itself for any future attacks. As the invader tried to gain a hold inside you, the lymph nodes swell and the LECs end up archiving the antigen information for later use. When the battle is won, the information is shared with the troops to keep them at the ready.

This information also has great potential to be used in vaccination research. With this knowledge in hand, scientists may be able to focus on developing stronger memory to reduce or prevent waning. This eventually may lead to improved versions of current vaccine options, such as those against the mumps virus. This study also may open the door to develop new vaccines. By focusing on developing memory over simply priming an attack, we may be able to find ways to keep us safe from pathogenic intruders in the future, including some for which we currently have no vaccine option.

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