The training of PhD students and early-career scientists is largely an apprenticeship in which the trainee associates with an expert to become an independent scientist. But when is a PhD student ready to graduate, a postdoctoral scholar ready for an independent position, or an early-career scientist ready for advanced responsibilities? Research training by apprenticeship does not uniformly include a framework to assess if the trainee is equipped with the complex knowledge, skills and attitudes required to be a successful scientist in the 21st century. To address this problem, we propose competency-based assessment throughout the continuum of training to evaluate more objectively the development of PhD students and early-career scientists.
Superantigens have been extremely helpful tools in exploring fundamental questions in immunobiology including mechanisms of cell activation, tolerance, and autoimmunity. Until recently, attention has been focused exclusive on T-cell superantigens. However, new data suggest that there are superantigens that directly activate B cells. By definition, these agents (1) stimulate a high frequency of B cells, (2) target B cells that have restricted usage of VH or VL family genes, and (3) bind to immunoglobulins outside the sites that bind conventional antigens. A candidate B-cell superantigen that has received considerable attention in this laboratory is staphylococcal protein A. This agent is best known to the immunologist because of its ability to bind to the Fc fragment of IgG. This binding has been localized to two alpha-helical structures on each of four or five homologous regions that comprise the extracellular domain of protein A. However, it is now clear that protein A contains a second site that binds to determinants on the Fab regions of certain immunoglobulins independently of their heavy-chain isotype. In man this so-called alternative site appears to bind only to immunoglobulins that utilize heavy-chain genes of the VH3 subfamily. In the mouse this type of binding is restricted to immunoglobulins using heavy chains belonging to the S107 and J606 VH families. In this review, we examine the growing list of microbial products that dominate B-cell superantigenic properties. Using staphylococcal protein A as a model for a B-cell superantigen, we consider the potential impact of this novel class of antigens on the immune response. We focus on the ability of B-cell superantigens to influence the expression of the B-cell repertoire. In addition, we consider the hypothesis that the interaction of a B-cell superantigen with its reactive serum immunoglobulins activates the classical complement cascade and thus represents a powerful stimulant of tissue inflammation.
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