Formation of supramolecular activation clusters on fresh ex vivo CD8+ T cells after engagement of the T cell antigen receptor and CD8 by antigen-presenting cells.
Upon productive interaction of CD4 T cells with antigen-presenting cells (APCs), receptors and intracellular proteins translocate and form spatially segregated supramolecular activation clusters (SMACs). It is not known whether SMACs are required for CD8 T cell activation. CD8 T cells, unlike CD4 T cells, can be activated by a single peptide-MHC molecule, or by purified monovalent recombinant peptide-MHC molecules. We studied, by three-dimensional digital microscopy, cell conjugates of fresh ex vivo CD8 T cells (obtained from OT-1 mice, which are transgenic for T cell antigen receptor reactive with the complex of H-2K(b) and the ovalbumin octapeptide SIINFEKL) and peptide-pulsed APCs. Remarkably, even in T cell:APC conjugates that were formed in the presence of the lowest concentration of peptide that was sufficient to elicit T cell proliferation and IFN-gamma production; the theta isoform of protein kinase C was clustered in a central SMAC, and lymphocyte function-associated antigen 1 and talin were clustered in the peripheral SMAC. Conjugation of T cells to APCs that were pulsed with concentrations of peptide smaller than that required to activate T cells was greatly reduced, and SMACs were not formed at all. APCs expressing mutant H-2K(b) (Lys(227)) molecules that do not bind CD8 were unable to form stable conjugates with these T cells, even at high peptide concentrations. Thus, although CD8 and CD4 T cells may display different sensitivity to the concentration and oligomerization of surface receptors, SMACs are formed and seem to be required functionally in both cell types. However, unlike CD4 T cells, which can form SMACs without CD4, CD8 T cells from OT-1 transgenic mice depend on their coreceptor, CD8, for the proper formation of SMACs.
Potter
T A
TA
Integrated Department of Immunology, National Jewish Medical and Research Center and the University of Colorado Health Sciences Center, Denver, CO 80206, USA. pottert@njc.org
Grebe
K
K
Freiberg
B
B
Kupfer
A
A
D000818:Animals; D000938:Antigen-Presenting Cells / Q000502:physiology*; D015704:CD4 Antigens / Q000502:physiology; D016827:CD8 Antigens / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D006183:H-2 Antigens / Q000502:physiology; D008213:Lymphocyte Activation; D051379:Mice; D008822:Mice, Transgenic; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*
D015704:CD4 Antigens; D016827:CD8 Antigens; D016207:Cytokines; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D011948:Receptors, Antigen, T-Cell