SummaryUsing granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin 4 we have established dendritic cell (DC) lines from blood mononuclear cells that maintain the antigen capturing and processing capacity characteristic of immature dendritic cells in vivo. These cells have typical dendritic morphology, express high levels of major histocompatibility complex (MHC) class I and class II molecules, CD1, Fcq, RII, CD40, B7, CD44, and ICAM-1, and lack CD14. Cultured DCs are highly stimulatory in mixed leukocyte reaction (MLR) and are also capable of triggering cord blood naive T cells. Most strikingly, these DCs are as efficient as antigenspecific B cells in presenting tetanus toxoid (TT) to specific T cell clones. Their efficiency of antigen presentation can be further enhanced by specific antibodies via FoR-mediated antigen uptake. Incubation of these cultured DCs with tumor necrosis factor o~ (TNF-o 0 or soluble CD40 ligand (CD40L) for 24 h results in an increased surface expression of MHC dass I and class II molecules, B7, and ICAM-1 and in the appearance of the CD44 exon 9 splice variant (CD44-vg); by contrast, Fc'yRII is markedly and sometimes completely downregulated. The functional consequences of the short contact with TNF-c~ are an increased T cell stimulatory capacity in MLR, but a 10-fold decrease in presentation of soluble TT and a 100-fold decrease in presentation of TT-immunoglobulin G complexes.

Naive T lymphocytes travel to T-cell areas of secondary lymphoid organs in search of antigen presented by dendritic cells. Once activated, they proliferate vigorously, generating effector cells that can migrate to B-cell areas or to inflamed tissues. A fraction of primed T lymphocytes persists as circulating memory cells that can confer protection and give, upon secondary challenge, a qualitatively different and quantitatively enhanced response. The nature of the cells that mediate the different facets of immunological memory remains unresolved. Here we show that expression of CCR7, a chemokine receptor that controls homing to secondary lymphoid organs, divides human memory T cells into two functionally distinct subsets. CCR7- memory cells express receptors for migration to inflamed tissues and display immediate effector function. In contrast, CCR7+ memory cells express lymph-node homing receptors and lack immediate effector function, but efficiently stimulate dendritic cells and differentiate into CCR7- effector cells upon secondary stimulation. The CCR7+ and CCR7- T cells, which we have named central memory (TCM) and effector memory (TEM), differentiate in a step-wise fashion from naive T cells, persist for years after immunization and allow a division of labour in the memory response.

immunology letters to nature 34 asymmetric unit (molecule B). Density for the other two molecules was broken and hard to interpret. The skeleton for molecule B was used to generate a molecular envelope for NCS averaging. Initial rotation matrices describing the relative orientations of molecules A, B and C were calculated from the heavy-atom sites (mercury bound to five sites in each of the three molecules). NCS averaging with DM 25 was used to improve phases at 2.7 Å resolution, and then extend phases to 2.2 Å , the limit of the native data set. The resulting electron density map was readily interpretable (Fig. 2). A model including residues 47-351 of each of the three molecules was built using the graphics program O 26 . No electron density is seen for 24 residues at the amino terminus. The model was refined using simulated annealing and positional refinement in X-PLOR 27 , with tight NCS restraints. The model includes 669 water molecules, which were positioned by using the program ARP (V.Lamzin). An overall thermal B factor and tightly restrained individual B factors were refined, and a bulk-solvent model was incorporated. Crystallographic R values and stereochemical parameters are presented in Table 1.The structure of the Cbl-N/ZAP70 phosphopeptide complex was determined by molecular replacement with the program AmoRe 28 . Use of the complete unliganded Cbl-N structure as a search model yielded clear rotation and translation peaks, and maps phased with the appropriately positioned model revealed strong electron density for the 4H and EF-hand domains, but no interpretable density for the SH2 domain. The model was therefore broken into two fragments (residues 47-265 and residues 266-351), and the rotation and translation searches were repeated with each fragment. The 4H/EF-hand fragment yielded a solution essentially identical to that from the intact model. The SH2 domain was then positioned using translation searches conducted in the context of the appropriately positioned 4H/EF-hand fragment. After rigid-body and positional refinement using X-PLOR 27 , electron density maps calculated with the combined model revealed clear density for all domains, and readily interpretable density for the bound ZAP-70 phosphopeptide. After construction of the peptide, the structure was refined with iterative cycles of manual refitting and simulated annealing and positional refinement in X-PLOR (Table 1). Restrained individual temperature factors were refined. The model includes residues 47-351 of c-Cbl, residues 289-297 of ZAP-70, and 358 water molecules. Figure 1a was prepared with MOLSCRIPT 29 , Fig. 2 with program O 26 , and Figs 1e and 3 with GRASP 30 . Illustrations

The memory T cell pool functions as a dynamic repository of antigen-experienced T lymphocytes that accumulate over the lifetime of the individual. Recent studies indicate that memory T lymphocytes contain distinct populations of central memory (TCM) and effector memory (TEM) cells characterized by distinct homing capacity and effector function. This review addresses the heterogeneity of TCM and TEM, their differentiation stages, and the current models for their generation and maintenance in humans and mice.

Researchers around the world are developing more than vaccines (DNA/mRNA/wholevirus/viral-vector/protein-based/repurposed vaccine) against the SARS-CoV-2 and 21 vaccines are in human trials. However, a limited information is available about which SARS-CoV-2 proteins are recognized by human Band T-cell immune responses. Using a comprehensive computational prediction algorithm and stringent selection criteria, we have predicted and identified potent Band T-cell epitopes in the structural proteins of SARS-CoV and SARS-CoV-2. The amino acid residues spanning the predicted linear B-cell epitope in the RBD of S protein (370-NSASFSTFKCYGVSPTKLNDLCFTNV-395) have recently been identified for interaction with the CR3022, a previously described neutralizing antibody known to neutralize SARS-CoV-2 through binding to the RBD of the S protein. Intriguingly, most of the amino acid residues spanning the predicted B-cell epitope (aa 331-NITNLCPFGEVFNATRFASVYAWNRK-356, 403-RGDEVRQIAPGQTGKIADYNYKLPD-427 and aa 437-NSNNLDSKVGGNYNYLYRLFRKSNL-461) of the S protein have been experimentally verified to interact with the cross-neutralizing mAbs (S309 and CB6) in an ACE2 receptorS protein interaction independent-manner. In addition, we found that computationally predicted epitope of S protein (370-395) is likely to function as both linear B-cell and MHC class II epitope. Similarly, 403-27 and 437-461 peptides of S protein were predicted as linear B cell and MHC class I epitope while, 177-196 and 1253-1273 peptides of S protein were predicted as linear and conformational B cell epitope. We found MHC class I epitope 316-GMSRIGMEV-324 predicted as high affinity epitope (HLA-A*02:03, HLA-A*02:01, HLA-A*02:06) common to N protein of both SARS-CoV-2 and SARS-CoV (N317-325) was previously shown to induce interferon-gamma (IFN-γ) in PBMCs of SARS-recovered patients. Interestingly, two MHC class I epitopes, 1041-GVVFLHVTY-1049