Class II antigen-specific murine cytolytic T lymphocytes (CTL). I. Analysis of bulk populations and establishment of Lyt-2+L3T4- and Lyt-2-L3T4+ bulk CTL lines.

Murine allogeneic cytolytic T lymphocytes (CTLs), including long-term bulk CTL lines, were induced in I-region-incompatible combinations of strains in vitro in order to study the phenotypes of class II major histocompatibility complex (MHC) antigen-specific CTLs, as well as the possible functional involvement of accessory cell interaction molecules such as Lyt-2 and L3T4. This report shows that class II-specific allogeneic CTL populations consist of two types of T cells. Lyt-2+L3T4- (2+4-) and Lyt-2-L3T4+ (2-4+), in variable proportions depending on the strain combination, that in vitro bulk CTL lines with each of these phenotypes can be established, that the killing function of 2-4+ CTL is sensitive to the blocking effect of anti-L3T4 antibodies, suggesting functional involvement of this molecule in the CTL-target interaction, that anti-Lyt-2 antibodies fail to block killing by 2+4- cells, suggesting that such CTLs do not utilize this molecule in their killing function, and that while I-A-specific CTLs of both phenotypes are detectable, 2-4+ cells could not be detected among I-E-specific CTL populations.