At 8, 15, and 39 days post-infection or -immunization (dpi) we analyzed CD4+ T cells in draining lymph nodes–pooled inguinal and lumbar (dLN) following i.m. rGP immunization or mediastinal (medLN) following i.n. LCMV infection–and spleens by staining with the LCMV I-Ab:gp66-77 MHC class II tetramer. Here, CD4 is linked to infection.