CD4 and infection: As previously observed [17, 22], analysis of thymic differentiation of DN, DP and SPs thymocytes regarding CD4 and CD8 markers during the acute infection, showed a huge decrease in the percentages (Figure 2B and 2C) and total numbers (Figure 2D) of DP thymocytes, starting at 13 d.p.i. and partially recovering later in infection.