RT Journal Article SR Electronic T1 Cutting Edge: Precursor Frequency Affects the Helper Dependence of Cytotoxic T Cells JF The Journal of Immunology JO J. Immunol. FD American Association of Immunologists SP 977 OP 980 DO 10.4049/jimmunol.168.3.977 VO 168 IS 3 A1 Mintern, Justine D. A1 Davey, Gayle M. A1 Belz, Gabrielle T. A1 Carbone, Francis R. A1 Heath, William R. YR 2002 UL http://www.jimmunol.org/content/168/3/977.abstract AB Generation of CTL immunity often depends on the availability of CD4 T cell help. In this report, we show that CTL responses induced by cross-priming can be converted from CD4-dependent to CD4-independent by increasing the frequency of CTL precursors. In the absence of CD4 T cells, high numbers of CTL precursors were able to expand in number and become effector CTL. The ability of high frequencies of CD8 T cells to override help was not due to their ability to signal CD40 via expression of CD154. These findings suggest that when precursor frequencies are high, priming of CD8 T cell responses may not require CD4 T cell help.