Figure 6.

Frequency of CD49d^high CD4⁺ T cells were positively correlated with anti-human blood group A antibody titer. (A) Follicular helper T cells, CD49d^high CD4⁺ T cells, and CD49d^low CD4⁺ T cells were gated from human peripheral blood lymphocytes using CD4, CD49d, CXCR5, and PD-1. (B) Correlations between the frequency of each population and anti-human blood group A IgM/IgG titers are shown. Anti-A IgM titer was positively associated with the frequency of CD49d^high CD4⁺ T cells (P = 0.0059; r = 0.4083) and negatively correlated with the frequency of CD49d^low CD4⁺ T cells (P = 0.0069; r = −0.4017). However, neither CD49d^high CD4⁺ T cells nor CD49d^low CD4⁺ T cell frequencies correlated with anti-A IgG titer. There was no correlation between the frequency of follicular helper T cells and anti-A antibody titer. Correlations were analyzed by Pearson’s correlation analysis.