Transcriptional analysis of human blood CXCR5+ CD4 T cell populations

The vast majority of currently licensed human vaccines work on the basis of long-term protective antibody responses. Generation of long term humoral immunity is a complex process predominantly dependent on germinal centers and CD4 T cell help to B cells. Follicular helper T cells (Tfh) are the specialized CD4 T cells for B cell help. However, whether such cells develop memory in humans and can be tracked in human blood has been enigmatic. We identified a subpopulation of blood CXCR5+ PD-1+CXCR3- resting CD4 T cells that are most related to Tfh cells of lymphoid tissue by gene expression profile and phenotype. Functional analysis showed that these memory Tfh cells were specialized for helping B cells. Moreover, these cells correlate with a clinically important outcome: development of potent neutralizing antibodies against HIV in HIV+ individuals. CD4 T cells were enriched from fresh blood of 5 normal donors by magnetic beads negative selection. Following enrichment, CD14-CD16-CD19-CD8-CD4+CD45RA- cells from each donor were FACS sorted into the following 5 populations: CXCR5-, CXCR5+PD1+CXCR3-, CXCR5+PD1+CXCR3+, CXCR5+PD1-CXCR3-, and CXCR5+PD1-CXCR3+. The gene expression profile of each cell population was determined.