Low molecular weight B cell growth factor (BCGF) and a monoclonal antibody (MHM6) to the 45-kDa, B lineage-restricted, CD23 activation antigen (BLAST-2; EBVCS) were found to be indistinguishable in their biological effects. Individually, both augmented DNA synthesis in activated, but not resting, B lymphocytes while no additional enhancement resulted from using the two agonists in combination. Furthermore, by increasing the expression of Tac, both MHM6 and BCGF promoted activated B cells to respond more vigorously to the late addition of recombinant interleukin 2. The presence of BCGF during B cell activations was found to down-regulate the expression of the CD23 antigen while the coating of activated cells with MHM6 antibody diminished their capacity to absorb BCGF activity. The findings demonstrate that CD23 and a low molecular weight BCGF deliver a comparable growth-promoting signal to activated B cells. A possible relationship between CD23 and the receptor for the low molecular weight BCGF is discussed.

CD23,p45 (BLAST-2,EBVCS) is a 45-kDa lineage-restricted antigen which appears on the surface of human B cells shortly after activation. A monoclonal antibody (MHM6) to CD23,p45, as well as a polyclonal rabbit antibody raised against the purified antigen were found to promote DNA synthesis in purified tonsillar B cells which had been activated with phorbol ester. Interleukin 1, which was not, by itself, stimulatory for either resting or activated B cells, significantly augmented the growth-promoting properties of MHM6. Kinetic studies indicated that while MHM6 exerted its influence in early G1, interleukin 1 acted later in the cycle just prior to the entry of cells into S phase. The findings demonstrate a role for CD23,p45 in triggering the progression of activated B lymphocytes through the G1 phase of the cell cycle. The possibility that this antigen serves as a receptor for a B cell stimulatory factor is discussed.

CONTEXT Completion of a rating questionnaire is the method used most frequently to evaluate a teacher's performance. Questionnaires that largely assess Ôhigh-inferenceÕ teaching characteristics, such as ÔenthusiasmÕ and ÔfriendlinessÕ, require the observer to make a judgement about the teacher but do not describe what the teacher actually did and so have limited use in providing feedback. Measures of Ôlow-inferenceÕ teaching behaviours (i.e. those that are concrete and observable), such as frequency, amount or types of verbal interaction, do not demonstrate how these are linked to good teaching.OBJECTIVES To describe high-inference teacher characteristics and define the associated lowinference behaviours.METHODS A purposive sample of consultants, postgraduate and undergraduate students, nurse lecture practitioners and patients were selected for semistructured interviews using repertory grids and critical incidents to elicit preferred characteristics and behaviours of clinical teachers. Interviews were audiotaped, transcribed and then content-analysed using a framework to pair teachers' characteristics and their behaviours.RESULTS We identified a variety of preferred highinference characteristics and their associated observable and recordable low-inference behaviours.DISCUSSION We carried out a study that included all participants in clinical teaching and found that participants differed in their preferred characteristics and behaviours. It is important for future research to look at behaviours interdependently, rather than alone, and to take into account the evidence that participants tend to infer characteristics rather than think in terms of behaviours. This information will be used to inform the development of a formative tool for evaluating clinical teaching.

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Treatment of Daudi B-lymphoblastoid cells with low concentrations of either natural or recombinant human alpha-interferons inhibits cell proliferation and modulates the expression of a number of cell-surface antigens. Using a panel of monoclonal antibodies (MAbs) identifying determinants expressed at the surface of normal plasma cells, and polyclonal antibodies against surface and cytoplasmic immunoglobulin, we have found that growth inhibition is accompanied by plasmacytoid differentiation. Assays of growth stimulation of heterologous cells indicate that the culture medium from interferon-treated Daudi cells contains substantially more B-cell growth factor activity than that from control cells. However, the interferon-treated cells exhibit an impaired ability to respond to both these autocrine factors and exogenous factors produced by another Burkitt lymphoma line. These findings show that, in the case of Daudi cells, growth inhibition by interferons is closely associated with both terminal differentiation and a refractoriness to growth factors. In this system IFN-alpha may therefore be considered to be a B-cell differentiation factor, suggesting a possible basis for the anti-proliferative effects observed with certain human B-cell malignancies.