No abstract

In vitro and in vivo responses to lipopolysaccharide (LPS) and various other bacterial immunostimulants were compared in c3H/He low-responder mice. The principal findings were as follows. (i) Their splenic lymphocytes were stimulated by various gram-negative mitogens such as an Escherichia coli peptidoglycan, a detoxified derivative of LPS, and even endotoxins extracted by trichloroacetic acid that are known to contain protein; spleen cells of these mice were also transformed by two other B-cell mitogens extracted from acid-fast organisms. (ii) Their macrophages were refractory to LPS and weakly responsive to a mycobacterial prepartion. (iii) LPS failed to elicit nonspecific resistance in these mice against Klebsiella pneumoniae infection. (iv) Endotoxin extracted by trichloroacetic acid and a mycobacterial preparation that could increase nonspecific resistance to infection in other strains did not protect C3H/He mice against a challenge by K. pneumoniae, although both prepartions could evoke nonspecific responses of B cells in this low-responder subline.

No abstract

The V beta 8.3-specific superantigenic lectin Urtica dioica agglutinin (UDA) was used to delete the V beta 8.3+ T cells in MRL lpr/lpr mice. In contrast to the systemic lupus erythematosus-like pathology which progresses with age in the phosphate-buffered saline-injected MRL lpr/lpr controls, UDA-treated animals did not develop overt clinical signs of lupus and nephritis. The pathogenic T cell clones thus reside within the V beta 8.3+ T cell population, which includes an expanded T cell clone described previously. Finally, UDA alters the production of autoantibodies in a sex-dependent manner.

We have used a new polymerase chain reaction-based technique to analyze at the clonal level the CDR3 diversity and the J beta usage associated with the V beta-dependent T cell receptor (TCR) recognition of two superantigens: the staphylococcal enterotoxin B and the Urtica dioica agglutinin. Our results show that subset of J beta elements is preferentially expanded in a given V beta family, independently of the nature of the superantigen. By contrast, the CDR3 loop does not contribute significantly to the T cell expansion induced by the superantigens. We conclude that the J beta segment of the TCR beta chain, but not the CDR3 region, participates in superantigen binding, presumably by influencing the quaternary structure of the TCR beta chain.