Delivery of effector proteins is a process widely used by bacterial pathogens to subvert host cell functions and cause disease. Effector delivery is achieved by elaborate injection devices and can often be triggered by environmental stimuli. However, effector export by the L. pneumophila Icm/Dot Type IVB secretion system cannot be detected until the bacterium encounters a target host cell. We u...

During an immune response, most effector T cells die, whereas some are maintained and become memory T cells. Factors controlling the survival of effector CD4 + and CD8 + T cells remain unclear. In this study, we assessed the role of IL-7, IL-15, and their common signal transducer, STAT5, in maintaining effector CD4 + and CD8 + T cell responses. Following viral infection, IL-15 was required to m...

The adaptive immune response of human CD8 T cells to invading pathogens involves the differentiation of naive cells into memory and effector cells. However, the lineage relationship between memory and effector cells and the differentiation of CD8 T cells into distinct subsets of effector cell subpopulations are subjects of considerable debate. CD7 identifies three populations of CD8 T cells: CD...

Two prototypic types of virus-specific CD8(+) T cells can be found in latently infected individuals: CD45R0(+)CD27(+)CCR7(-) effector-memory, and CD45RA(+)CD27(-)CCR7(-) effector-type cells. It has recently been implied that CD45RA(+)CD27(-)CCR7(-) T cells are terminally differentiated effector cells and as such have lost all proliferative capacity. We show in this study, however, that stimulat...

This study describes the effects of incubating antibody-forming cells (AFC), either as mass cell suspensions, or as single AFC in microdroplets, with antigens against which the cells display specificity. Most of the work was done with hapten-specific anti-DNP-AFC, but AFC with specificity against flagellar antigens or fowl gamma globulin (FGG) were also included. It was noted that 30-min incuba...

The effector cell mechanisms involved in allograft or tumor rejection are still controversial (1) . Sprent et al . (2) recently demonstrated that injection of Lyt-2' cells (positively purified by the panning method) into adult, thymectomized, bone marrow-reconstituted (ATXBM)' B6 mice resulted in rejection of skin from the H-2Kb mutant strain of B6.C-H-2bm' (bmI), but not the H-21Ab mutant stra...