Scientists know surprisingly little about how flu vaccines actually work. Now, new research suggests that a population of T cells appears in the blood after seasonal influenza vaccination and may boost the body’s development of protective antibodies against the flu.
Following two small groups of children and adults for three years, Salah-Eddine Bentebibel and colleagues at Baylor Research Institute, along with teams from Baylor University, The Research Institute at Nationwide Children’s Hospital, and Mount Sinai School of Medicine, discovered a special subgroup of T cells that appear in blood after flu vaccination. These CD4+ T cells express three markers—CXCR5, CXCR3, and ICOS—and are correlated with the development of protective antibodies against flu. Up to 60% of these ICOS+CXCR3+CXCR5+CD4+ T cells were specific for influenza antigens and expressed interleukin-2 (IL-2), IL-10, IL-21, and interferon-γ upon antigen stimulation.
The authors found that these T cells work by helping pre-existing memory B cells to boost antibody production. The variation of memory B cells against the flu normally increases with age, through vaccination, and exposure to the virus year after year. Therefore, it makes sense that elderly people generally have an ample supply of memory B cells that are ready to fight many different kinds of flu.
Failure of the elderly to induce a protective antibody response after flu vaccination may be associated with the failure to induce this special group of T cells that express the three markers, the authors suggest. Further studies aimed at findings ways to harness these T cells could potentially improve vaccine design.
This study is published in Science Translational Medicine in a paper titled “Induction of ICOS+CXCR3+CXCR5+ TH Cells Correlates with Antibody Responses to Influenza Vaccination”.