Scientists in Germany say they have pinpointed the mechanism by which Salmonella infections can reduce the incidence of asthma in mice. They point out that their research (“Salmonella Typhimurium Infection Induced CD11b+Gr1+ Cells Ameliorate Allergic Airway Inflammation”), which appears ahead of print in Infection and Immunity, should open up new avenues of research that could lead to treatments.
The incidence of allergies has risen greatly over the past few decades. One theory, the “hygiene hypothesis,” holds that this is due to the modern obsession with cleanliness, which is leaving immune systems inexperienced and improperly developed. Earlier research had suggested that there is a reduced incidence of asthma in children who have been infected with Salmonella.
In their study, as per previous research, the investigators saw that Salmonella infection correlated with reduced airway inflammation, explained first author Venkateswaran Ganesh, from the Institute of Infection Immunology, Twincore, Centre for Experimental and Clinical Infection Research. The organization is a joint venture between the Hannover Medical School and the Helmholtz Centre for Infection Research. Ganesh traced the reduction in inflammation to reduced production of the inflammatory compound interleukin-4, which is produced by T helper-2 cells.
Ganesh and colleagues found that an increase in production of a myeloid immune cell was responsible for regulating the T helper-2 cells to produce less IL-4.
“We observed a significant 37 increase in CD11b+Gr1+ myeloid cell population in mice after infection with S. Typhimurium. Using in vitro and in vivo studies we confirmed that these myeloid cells reduce airway 39 inflammation by influencing Th2 cells,” wrote the investigators. “Further characterization showed that the CD11b+Gr1+ myeloid cells exhibited their inhibitory effect by altering GATA-3 expression and IL-4 production by Th2 cells. These results indicate that the expansion of myeloid cells upon S. Typhimurium infection could potentially play a significant role in curtailing allergic airway inflammation.”
The team concluded that this research could lead to treatments based on the use of commensal bacteria resembling Salmonella as probiotics, or the application of myeloid cells as therapeutics.