An important issue for immunologists is the difference between the two main processes that determine the mature repertoire of T-cell receptors, termed positive and negative selection. Recent papers have addressed the role of self-peptides in the process of positive selection.

We demonstrate that purified interleukin 2 (IL-2) can directly upregulate IL-2 receptor expression on phytohemagglutinin-activated T lymphocytes maintained in culture until IL-2 receptor expression had markedly declined. The IL-2-induced increase in IL-2 receptor number is maximal within 12 hr, requires new RNA and protein synthesis, and is mediated by an interaction of ligand with the high-aff...

Allelic exclusion of lymphocyte antigen receptor chains has been hypothesized as a mechanism developed by the immune system to ensure efficient lymphocyte repertoire selection and tight control of lymphocyte specificity. It was effectively shown to be operative for both the immunoglobulin (Ig) and the T cell receptor (TCR) beta chain genes. Our present observations suggest that close to 1% of h...

The immune system has evolved a number of sophisticated molecular mechanisms that assure the maintenance of a highly diverse repertoire of lymphocyte receptors. In view of the vast potential for V region diversity, the immune system must judiciously choose specificities that are of greatest value for expression in the lymphocyte receptor repertoire. Indeed, .the. challen~e. to immunologists no ...

The effects of D-penicillamine on T-lymphocytes (rosette forming cells) and B-lymphocytes (surface IgG- and surface IgM-bearing cells) in peripheral blood of 13 patients with classical or definite rheumatoid arthritis were investigated at 4 weeks, 12 weeks and 24 weeks of treatment. At the same time, the determination of the concentrations of serum immunoglobulins and RA tests were carried out,...

A costimulatory signal in addition to an Ag-specific stimulus is required for optimal activation of T lymphocytes. CD28, the primary positive costimulatory receptor on T cells, has two identified ligands, B7-1 and B7-2. Whether B7-1 and B7-2 have identical, overlapping, or distinct functions remains unresolved. In this study, we show that mice lacking B7-2 were unable to generate CTL responses ...

Proliferative renewal of memory CD8 T cells is essential for maintaining long-term immunity. In this study, we examined the contributions that various tissue microenvironments make toward the homeostatic proliferation of Ag-specific memory CD8 T cells. We found that dividing memory T cells were present in both lymphoid and nonlymphoid tissues. However, the bone marrow was the preferred site for...