Pattern of costimulatory molecules expression on DO11

Pattern of costimulatory molecules expression on DO11.10 T cells before and after stimulation with antigen. the long-lived cells-driven memory responses were measured. The findings indicate that B cells and CD8+DCs sustained elevated frequencies of long-lived T cells which yielded rapid and robust memory responses upon re-challenge with sub-optimal dose of Ag. Furthermore, both types of APCs had significant Programmed Death Ligand 2 (PD-L2) expression prior to Ag stimulation, which was maintained at a high level during presentation of Ag to T cells. Blockade of PD-L2 interaction with its receptor Programmed Death (PD-1) nullified the development of memory responses. These previously unrecognized findings suggest that targeting specific APCs for Ag presentation during vaccination could prove effective against microbial infections. == Introduction == Immunological memory is the cardinal feature of the immune system that provides the fundamental basis for vaccine development (1-5). An initial encounter with the cognate antigen triggers nave T cells to differentiate into effectors that engage in microbial clearance (1-5). Upon completion of this task the cells enter a contraction phase during which most effectors cells undergo apoptosis. Very few of the effectors (1 in 105-106) do not undergo apoptosis but become long-lived microbe-specific memory cells that will respond to future infections (2,6). Despite the fact that few cells transit from effector to memory, the resulting increase in Ag-specific precursors enables rapid and robust responses against future encounters with the microbe (7-12). Most of the progress made to date on the development of T cell memory has involved the development of CD8+T cell memory and late phase memory responses. Much less is understood about Rabbit Polyclonal to NKX28 the development and maintenance of CD4+T cell memory. Also, little is known on how and when the decision to become a short-lived effector versus a long-lived memory cell is made (2,13-14). The low frequency of effectors that transit to memory and the lack of specific markers to track memory precursors have hindered progress in this field (15-16). Understanding the events that direct the effector to memory transition will likely aid in the development of effective vaccination strategies (17). We have previously shown thatin vivoexposure of TCR transgenic T cells to ovalbumin 323-339 peptide (OVA) yields effector T cells, some of which produce significant IFN while others secrete rather modest levels of IFN (18). Interestingly, the IFN producing effectors gave rise to memory precursors that sustained rapid and robust memory responses while those with reduced IFN yielded delayed and moderate memory responses. Given that a homogeneous population of nave TCR transgenic T cells was used, the assorted memory responses Fludarabine (Fludara) may reflect differential antigen presentation by various APCs rather than the function of T cell intrinsic factors. The results presented here demonstrate that B cells and the CD8+DC subset support transition from effector to memory and generate significant memory precursors that sustain rapid and robust responses, the hallmark of memory (19-24). Fludarabine (Fludara) Furthermore, both cells express higher levels of PD-L2, a ligand for the negative regulator of T cell activation PD-1, in their resting state. This is maintained during presentation of OVA and blockade of the interaction between PD-L2 and PD-1 drastically reduced memory responses. Therefore, specific types of APCs such as B cells and CD8+DCs display an intrinsic expression of PD-L2 prior to and during presentation of antigen, thus supporting transition from effector to memory possibly by restraining hyperactivation of T cells. Fludarabine (Fludara) == Materials and Methods == == Mice == DO11.10/scid or DO11.10/RAG2/transgenic mice (H-2d) expressing a T cell receptor specific for OVA peptide were previously described (25). Balb/c mice (H-2d) were purchased from Harlan Sprague Dawley, Indianapolis, IN. MHC II/Balb/c mice (cAN 129 S6 (B6) Iitm1 Liz/) (H-2d) were purchased from Jackson Laboratories, Bar Harbor, ME. All animals were used in accordance with the guidelines of the University of Missouri institutional animal care and use committee. == Antigens == OVA peptide (SQAVHAAHAEINEAGR) encompasses.