CD44 and infection: As TFH cells evolve over time11,33, we assessed the early peak of TFH and GC B cell accumulation for each infection, defined by TFH and GC B cell frequency, in polyclonal TFH (CD3+CD4+CD44+Ly6C−CD162−CXCR5+PD-1+Bcl-6+) and Teff (CD3+CD4+CD44+Ly6C+CD162+CXCR5−PD-1−Bcl-6−) cell compartments after viral (acute Armstrong lymphocytic choriomeningitis virus (LCMV) or influenza A HKx31 H3N2 strain), helminth (Trichuris muris7 or Heligmosomoides polygyrus), and bacterial (Citrobacter rodentium) infections (Fig. 1a and Extended Data Fig. 1a,b).