Investigating heterogeneity within T follicular helper cells (TFH) population.

T follicular helper cells (TFH) are heterogenic population of CD4+ T cells, expressing CXCR5+ and PD-1+ on their surface. Their role is linked to supporting formation of germinal centres (GC) and these cells are thought to express high levels of PD-1 marker. Two models of immunisation were used to investigate the role of PD-1 low TFH. In Salmonella enterica infection high frequency of T follicular helper cells expressing low levels of PD-1 surface molecule are observed within first week of infection but GC do not appear until much a later stage (week 7-8). Sheep red blood cell immunisation (SRBC) gives rise to both TFH and GC B cells within first week of response and these TFH express low to high level of PD-1 molecule.

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