Research

Multiple mechanisms of immunosuppression by intestinal worms

Apparently, worms play it safe with respect to immunosuppression. At least the intestinal roundworm Strongyloides does so in an experimental infection of mice.

Microscopic image of the host intestinal mucosa during a worm infection.
Microscopic image of the host intestinal mucosa during a worm infection. Cross-section of invaginations of the mucosa, which serve to enlarge the bowel surface area for efficient absorption of nutrients. Cells stained in dark red are mast cells which enhance mucous production and peristalsis to expulse worms (Photography: Anja Kühl, Charité, Berlin).

On one hand, the worms directly inhibit central helper cells of the immune system (CD4+T lymphocytes) by increasing the numbers of inhibitory receptors (BTLA) on their surfaces. On the other hand, they cause a proliferation of regulatory T lymphocytes (Treg), which inhibit other immune cells including T helper lymphocytes. Deletion of either the inhibitory molecules on T helper cells or the regulatory T cells themselves increased the ability of mice to expel the worms from their intestines. In this experimental model, interleukin 9 played a pivotal role as a messenger molecule. It stimulated so-called mast cells, specialised immune cells in the intestinal mucosa which enhance bowel movements and mucous production to wash out the worms. Mast cells also greatly contribute to allergy-type immune reactions.

 


Blankenhaus B. et al., PLoS Pathog 2014, 10:e1003913;
Breloer M. et al., J Immunol 2015, 194:1413-6

Birte Blankenhaus, Wiebke Hartmann, Marie-Luise Eschbach, Martina Reitz, Yannick Brenz, Irma Haben, Thomas Jacobs, Minka Breloer and external co-operation partners (see publications)