The level of blood leukocytes in PNAS is related to the gut microbe

After treatments such as stem cell transplantation or chemotherapy, the composition of gut bacteria is essential
to promote the recovery of the number of neutrophils in the blood of mice.

White blood cells or granulocytes are part of the
innate immune system.
The most common type of granulocytes is neutrophils, which are phagocytes that destroy microorganisms
in the body.
A low neutrophil count in the blood is called neutropenia; This condition is common in leukemia or after
chemotherapy.
Neutropenia is known to induce granulogenesis, the process
by which granulocytes are formed.
However, the exact mechanism by which neutropenia drives granule production is not fully understood
.

A research team led by Associate Professor Daigo Hashimoto and Professor Takanori Teshima of Hokkaido University School of Medicine found that the gut microbiota plays a key role
in driving particle production in mouse models.
The results were published in PNAS
.

The process of increasing particle production above the homeostatic level can be divided into emergency particle generation, driven by the presence of bacteria, and reactive particle generation, which increases particle production
in the absence of infection by live microorganisms.
Reactive neutropoiesis
are known to occur after neutropenia caused by hematopoietic stem cell transplantation (SCT) or cancer chemotherapy.
The team wanted to understand the mechanism
by which neutropenia triggered reactive granulogenesis in both cases.

The team induced prolonged neutropenia in a mouse model and observed levels of cytokines (cell signaling molecules), known to be involved in
granulogenesis.
They found significant elevations in two cytokines: granulocyte colony-stimulating factor (G-CSF) and interleukin 17A (IL-17A).

They found that IL-17A is essential
for the recovery of neutrophils.
They confirmed that T cells are the main source of
IL-17A.

They were interested in studying whether the gut microbiome influences granule production, building on other studies showing that the gut microbiome and bone marrow hematopoiesis can influence
each other.
They found that the gut microbiome did upregulate reactive granule production through IL-17A secreted by T cells, and also found that prolonged neutropenia altered the gut microbiome
.
They determined that it was this change in microbiome composition that enhanced reactive particle production
.

This study proves that the change of the gut microbiome caused by neutropenia stimulates reactive neutrophil production in the bone marrow through IL-17A secreted by T cells, promoting neutrophil recovery
.
Future work will focus on clinical trials to test whether such crosstalk exists in humans; Other avenues include developing antibiotic formulations that leave the bacteria that support particle formation intact
.

Reactive granulopoiesis depends on T-cell production of IL-17A and neutropenia-associated alteration of gut microbiota