Neal Roehm

T cell tolerance by clonal elimination in the thymus

The monoclonal antibody KJ23a reacts with T cell receptors utilizing the V beta segment V beta 17a. T cells bearing V beta 17a+ receptors react with very high frequency with the MHC class II protein, IE. In this paper we show that T cells expressing V beta 17a are selectively eliminated from the peripheral T cell and mature thymocyte pool of mice expressing IE, but are present in expected numbers in the immature thymocyte population of such animals. These results show that in normal animals tolerance to self-MHC is due to clonal elimination rather than suppression. In addition, they indicate that tolerance induction may occur in the thymus at the time immature thymocytes are selected to move into the mature thymocyte pool.

A T cell receptor Vβ segment that imparts reactivity to a class II major histocompatibility complex product

We have identified in mice an allele of a new T cell receptor V beta gene, V beta 17a, whose product is bound by the monoclonal antibody KJ23a. Over 90% of T cell hybridomas prepared from V beta 17a+ T cells of SWR mice respond to allogeneic forms of the IE class II MHC protein, indicating that V beta 17a has an appreciable affinity for IE regardless of the other components of the T cell receptor. These results suggest a bias in the germ-line T cell receptor repertoire toward recognition of MHC proteins and indicate that the V beta portion of the receptor may form the most important contact points with MHC ligands.

Nonspecific factors in B cell responses.

In common with many other groups, we have had a longstanding interest in the helper signals required by B cells during the course of an IgM response to sheep red blood cells (SRBC). This particular phenomenon has received a good deal of attention because of its apparent simplicity. Thus, early on it was shown that an apparently T-cell derived non-specific helper factor(s) was sufficient to drive B cell responses to SRBC, whereas other, antigen specific factors or T cells were needed for antibody to be made against protein-bound antigens (Dutton et al. 1971, Schimpl & Wecker 1972, Harwell et al. 1976a, b, Waldmann 1975). Later work defined a T cell product of molecular weight 30-40KD as the principal active stimulator (Watson et al. 1979, Schimpl et al. 1980). This factor was and is commonly called T cell replacing factor (TRF). More recently, experiments examining the synergy between various factors (Farrar et al. 1977, Hoffmann & Watson 1979) and using B cell preparations with lower levels of contaminating T cells (and macrophages (M0) in some cases) have shown that matters were not as simple as was once hoped. To illustrate this, in this paper we describe some of our recent experiments which have shown that several factors are needed for anti-SRBC responses, in cultures containing highly purified B cells.

Preparation and characterization of a “pan-reactive” rabbit anti-mouse T-cell receptor antiserum☆

A pan-reactive xenoantiserum to the mouse T-cell receptor was prepared by immunization of a rabbit with affinity purified mouse T-cell receptor material. The T-cell receptor of the chicken ovalbumin/IAd specific T-cell hybridoma, DO-11.10, was isolated by affinity chromatography using the clone-specific monoclonal antibody, KJ1-26. Immunoprecipitation with the rabbit antiserum and subsequent SDS-PAGE analysis of the material precipitated from lysates of surface radioiodinated T cells revealed the heterodimeric structure characteristic of the T-cell receptor from virtually every T-cell source examined. Flow cytofluorometric analysis of normal peripheral T cells and mature thymocytes of BALB/c and SJL mice indicated that most all T cells bear antigenic determinants recognized by the rabbit anti-mouse T-cell receptor antibodies. The AKR thymoma, BW5147, a common fusion parent used to generate functional T-cell hybridomas, notably lacks surface expression of a T-cell receptor molecule.

Expression of the Antigen-Specific MHC-Restricted T Cell Receptor

The genes and proteins of antigen-specific, MHC-restricted T cell receptors are now quite well understood, although little is currently known about the control of their expression. In this chapter we discuss various influences on the reactivity of peripheral T cells, and show that the germ line T cell receptor repertoire is probably read out randomly in immature, cortical thymocytes. Several factors affect expression on mature thymocytes and peripheral T cells. These include a selective process which occurs at the transition of immature to mature thymocytes, which may be selection for self-MHC restriction, and/or tolerance induction and is illustrated in the work presented here by blocking at this point with antireceptor antibodies, and by specific inhibition of maturation of immature thymocytes bearing a particular receptor allotype in an MHC-controlled fashion.