CD40 Ligand-Mediated Interactions Are Involved in the Generation of Memory CD8+ Cytotoxic T Lymphocytes (CTL) but Are Not Required for the Maintenance of CTL Memory following Virus Infection

AUTOR(ES)

Borrow, Persephone

FONTE

American Society for Microbiology

RESUMO

CD8+ cytotoxic T lymphocytes (CTL) play a key role in the control of many virus infections, and the need for vaccines to elicit strong CD8+ T-cell responses in order to provide optimal protection in such infections is increasingly apparent. However, the mechanisms involved in the induction and maintenance of CD8+ CTL memory are currently poorly understood. In this study, we investigated the involvement of CD40 ligand (CD40L)-mediated interactions in these processes by analyzing the memory CTL response of CD40L-deficient mice following infection with lymphocytic choriomeningitis virus (LCMV). The maintenance of memory CD8+ CTL precursors (CTLp) at stable frequencies over time was not impaired in CD40L-deficient mice. By contrast, the initial generation of memory CTLp was affected. CD40L-deficient mice produced lower levels of CD8+ CTLp during the primary immune response to LCMV than did wild-type controls, despite the fact that the LCMV-specific effector CTL response of CD40L-deficient mice was indistinguishable from that of control animals. The differentiation of naïve CD8+ T cells into effector and memory CTL thus involves pathways that can be discriminated from each other by their requirement for CD40L-mediated interactions. Expression of CD40L by CTLp themselves was not an essential step during their expansion and differentiation from naïve CD8+ cells into memory CTLp; instead, the reduction in memory CTLp generation in CD40L-deficient mice was likely a consequence of defects in the CD4+ T-cell response mounted by these animals. These results thus suggest a previously unappreciated role for CD40L in the generation of CD8+ memory CTLp, the probable nature of which is discussed.

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