Platelets and the Immune Response

I have often suspected it, but we now have fresh evidence that blood platelets have a role in the immune system as well as in thrombosis.

Freom the New Scientist:

When bacteria enter blood they rapidly become coated in platelets, says Dirk Busch at the University of Munich in Germany. These sticky cell fragments then direct bacteria to the spleen, where they are engulfed by dendritic cells – immune cells that trigger a full-blown immune response.

This process relies on the interaction between a platelet receptor called GPIb and a blood protein called C3, which sticks to bacteria. When mice bred to lack C3 were injected with Listeria monocytogenes, platelets failed to surround the bacteria. Instead, they were destroyed by a different immune cell, the macrophage.

Although the macrophages cleared the bacteria, the lack of C3 prevented the formation of immunological memory – which enables the immune system to remember foreign invaders and respond to a future attack. Ultimately, Busch says it might be possible to boost platelet response to improve vaccines.

Does boozing lower immunity?

From today's New Scientist

Alcohol suppresses immune cells, making heavy drinkers more vulnerable to infection

Too much alcohol dulls more than your wits. It also weakens your immune system and could make you more vulnerable to viruses.

Gyongyi Szabo at the University of Massachusetts Medical School in Worcester and colleagues exposed monocytes – white blood cells involved in the defence against infection – to chemicals that mimic viruses and bacteria. Half of the cells were also soused in the levels of alcohol that a person might have in their blood after quaffing four or five alcoholic drinks daily for a week.

When the over-the-limit cells were exposed to a virus mimic, they made only a quarter as much of the virus-fighting signalling molecule type-1 interferon as teetotal monocytes made. Monocytes exposed to alcohol and a bacterial chemical not only made half as much type-1 interferon as their abstemious equivalents, they also overproduced an inflammatory chemical called tumour necrosis factor-alpha that in high volumes can damage tissue.