Effect of activated CD4+ T cell killing on immune competence. (a) Serum titers (mean ± SEM, n = 5-7) of neutralizing antibodies (nAb) in FV-infected DTA, wild-type (WT) and B6 mice. P ≤ 0.018 and P ≤ 0.007 on days 21 and 28, respectively, between DTA mice and either WT or B6 mice. (b) FV-encoded glyco-Gag on the surface of infected erythroid precursor (Ter119+) cells in the same mice. Glyco-Gag+ Ter119+ cells were detected in four out of seven DTA mice. (c) Serum titers (mean ± SEM, n = 6-9) of nAb in IAV-infected DTA, WT and B6 mice. P = 0.002 between DTA and WT mice and P = 0.00003 between DTA and B6 mice on day 18. (d) Body weight changes in Pneumocystis murina-infected DTA, WT, B6 and MHC II-deficient (MHC II-/-) mice. P ≤ 0.04 between DTA and WT or B6 mice on weeks 16 and 17 after infection for body weight changes. Numbers within the plot denote the ratio of mice tested positive for P. murina at the end of the observation period (P = 0.004 between DTA and control mice).