Immune hematology

The study find that the A rare, short-lived population of immune cells in the bloodstream may serve as ‘periscopes’ to monitor immune status via lymph nodes deep inside the body, according to researchers in the Perelman School of Medicine at the University of Pennsylvania. Therefore Their findings are published this month in the Journal of Clinical Investigation (JCI). “This finding paves the way for using blood samples to provide a snapshot of whole-body immunity,” said the study’s co-first author Laura Vella. MD, Ph.D., a physician-scientist who performed this work in the lab of senior author E. John Wherry, Ph.D., chair of the department of Systems Pharmacology and Translational Therapeutics.

Immune cells in the bloodstream

Vella is also a pediatric infectious diseases physician at Children’s Hospital of Philadelphia (CHOP). Researchers say this work could help better define and monitor the condition of the immune system in vulnerable groups; but such as infants and small children, the elderly; patients taking immune-suppression drugs, and those with autoimmune-based disorders like inflammatory bowel disease (IBD).

“It’s as if we’re trying to find the toxins draining from a single pipe into the Great Lakes how do we find and characterize what is originating from that one spot in the water of an entire glacial lake?” Wherry said. “The cells we’re looking for in the bloodstream ;are 0.1% of all cell types circulating in the blood. But our ‘periscope’ allows us see what that rare cell type can tell us about immune system events that have happened in a distant part of the body.”

B cells in the germinal centers

The elusive cell population described in this study are T follicular helper cells (Tfh). These are a subset of immune T cells required for B cells in the germinal centers (GC) of lymph nodes to make antibodies that fight germs and other outside invaders. Some Tfh cells in lymph nodes uniquely express the surface receptor protein CXCR5 and the inhibitory molecule PD-1. Blood does contain some Tfh cells with theses markers; however, scientists have long debated whether Tfh cells exit lymph nodes and circulate in the blood with traces of their original markers.

“This finding paves the way for using blood samples to provide a snapshot of whole-body immunity;” said the study’s co-first author Laura Vella. MD, Ph.D., a physician-scientist who performed this work in the lab of senior author E. John Wherry; Ph.D., chair of the department of Systems Pharmacology and Translational Therapeutics. Vella is also a pediatric infectious diseases physician at Children’s Hospital of Philadelphia (CHOP).

Whole-body immunity

Researchers say this work could help better define and monitor the condition of the immune system in vulnerable groups; such as infants and small children, the elderly; patients taking immune-suppression drugs; and those with autoimmune-based disorders like inflammatory bowel disease (IBD).

“It’s as if we’re trying to find the toxins draining from a single pipe into the Great Lakes how do we find and characterize what is originating from that one spot in the water of an entire glacial lake?” Wherry said. Because “The cells we’re looking for in the blood stream are 0.1% of all cell types circulating in the blood. But our ‘periscope’ allows us see what that rare cell type can tell us about immune system events that have happened in a distant part of the body.”