CD4 and influenza: An adoptive transfer study using T cell-deficient recipient mice53 and a newer study using an influenza infection model in Cxcr5f/f CD4-Cre mice54 showed that it was possible for CXCR5-deficient CD4+ T cells to enter B cell follicles and form GC-Tfh cells, suggesting that some other signals allow for the GC localization of CXCR5-deficient cells.