Formation of a central supramolecular activation cluster is not required for activation of naive CD8+ T cells.
Although both naive and effector T lymphocytes interact with antigen-expressing cells, the functional outcome of these interactions is distinct. Naive CD8(+) T cells are activated to proliferate and differentiate into effector cytolytic T lymphocytes (CTL), whereas CTL interact with specific targets, such as tumor cells, to induce apoptotic death. We recently observed that several molecules linked to actin cytoskeleton dynamics were up-regulated in effector vs. naive CD8(+) T cells, leading us to investigate whether T cell differentiation is accompanied by changes in actin-dependent processes. We observed that both naive and effector CD8(+) T cells underwent T cell receptor capping and formed stable conjugates with antigen-specific antigen-presenting cells. However, the characteristics of the immunological synapse were distinct. Whereas accumulation of signaling molecules at the T cell/antigen-presenting cell contact site was detectable in both naive and effector CD8(+) T cells, only effector cells developed a central supramolecular activation cluster as defined by punctate focusing of PKC theta, phospho-PKC theta, and phospho-ZAP70. Extended kinetics, CD28 costimulation, and high-affinity antigenic peptide did not promote PKC theta focusing in naive cells. Nonetheless, naive CD8(+) T cells polarized the microtubule organizing center, produced IL-2, proliferated, and differentiated into effector cells. Our results suggest that the formation of a central supramolecular activation cluster is not required for activation of naive CD8(+) T cells and support the notion that one role of an organized immune synapse is directed delivery of effector function.
O'Keefe
James P
JP
Committee on Cancer Biology and Department of Pathology, University of Chicago, IL 60637, USA.
Blaine
Kelly
K
Alegre
Maria-Luisa
ML
Gajewski
Thomas F
TF
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology*; D002454:Cell Differentiation; D007376:Interleukin-2 / Q000032:analysis; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology
D007376:Interleukin-2; D012333:RNA, Messenger; D011948:Receptors, Antigen, T-Cell