Figure 1. Chronic phase of a P. chabaudi infection enhances CD4⁺ Memory T cell activation and expansion.

Mice were infected with 10⁵ P. chabaudi (AS). On days 30-34 one group of mice was treated with chloroquine (+CQ), which quickly eliminated the infection, while the other mice retained a chronic infection (-CQ). A) Half of each group was re-infected with 10⁵ P. chabaudi day 60 post-infection, and splenocytes were analyzed by flow cytometry on day 63 for CD4, CD44, CD62L and expression of the early activation marker CD69 (A–C) or incorporation of BrdU dosed into the water days 60–65 as an indicator of homeostatic proliferation (D, E), CD69 expression on central memory T cells (Tcm, CD44^hiCD62^lo) and effector memory T cells (Tem, CD44^hiCD62L^int/hi) are shown. Dotted lines represent chloroquine treated mice (+CQ) while bold lines represent chronic infection (-CQ). Data shown is the average of 4–5 mice per group and experiment was repeated twice with similar results. * indicates p≤0.05, ** p≤0.01.