Enhanced susceptibility to superantigen-associated streptococcal sepsis in human leukocyte antigen-DQ transgenic mice.

Bacterial superantigens are believed to cause septic shock, although, because of the lack of superantigen-sensitive infection models, proof that superantigenicity underlies shock pathogenesis is lacking. This work demonstrates a clear superantigen effect in septic shock resulting from bacterial infection. Transgenic expression of human leukocyte antigen (HLA)-DQ, but not HLA-DR, specifically augments lymphocyte responses to streptococcal pyrogenic exotoxin A (SPEA). HLA-DQ transgenic mice had increased mortality after administration of SPEA or infection with Streptococcus pyogenes. Immune activation during infection was HLA-DQ transgene-dependent and was manifested by Vbeta-specific T cell repertoire changes and widespread lymphoblastic tissue infiltration. Unlike earlier models, which used toxin-induced shock, these T cell superantigen responses and lymphoblastoid changes were observed during invasive streptococcal sepsis. Lymphoid activation was undetectable in HLA-DQ mice infected with an isogenic SPEA(-) strain, which proves that a single superantigen can play a role in sepsis pathogenesis.

Streptozotocin-induced diabetes in mice lacking alphabeta T cells.

Multiple low-dose streptozotocin (MD-STZ) is widely used for the experimental induction of diabetes, but, as non-obese diabetic (NOD)-scid/scid mice have been found to display enhanced susceptibility to MD-STZ, whether or not the model is genuinely autoimmune and T cell-mediated has been unclear. Mice bearing a targeted mutation of the T cell receptor (TCR) alpha-chain were therefore used to assess whether TCR alphabeta+ cells are involved in the diabetogenic effects of MD-STZ injections. Young NOD mice lacking TCR alphabeta cells, when given five daily injections of 40 mg/kg STZ, developed diabetes at low frequency (2/12), despite the widespread destruction of pancreatic islet cells. By comparison, most normal control mice became hyperglycaemic (12/23). We conclude that whilst much of the tissue destruction observed in this model is due to the direct toxic effect of STZ, a significant amount is also due to the action of TCR alphabeta cells tipping the balance between tolerable and clinically damaging action on islet cells.

A role of Hsp60 in autoimmune diabetes: analysis in a transgenic model.

A pathogenic role for self-reactive cells against the stress protein Hsp60 has been proposed as one of the events leading to autoimmune destruction of pancreatic beta cells in the diabetes of nonobese diabetic (NOD) mice. To examine this hypothesis, we generated transgenic NOD mice carrying a murine Hsp60 transgene driven by the H-2E alpha class II promoter. This would be expected to direct expression of the transgene to antigen-presenting cells including those in the thymus and so induce immunological tolerance by deletion. Detailed analysis of Hsp60 expression revealed that the endogenous gene is itself expressed strongly in thymic medullary epithelium (and weakly in cortex) yet fails to induce tolerance. Transgenic mice with retargeted Hsp60 showed overexpression of the gene in thymic cortical epithelium and in bone marrow-derived cells. Analysis of spontaneous T-cell responses to a panel of self and heterologous Hsp60 antigens showed that tolerance to the protein had not been induced, although responses to an immunodominant 437-460 epitope implicated in disease were suppressed, probably indicating an epitope shift. This correlated with changes in disease susceptibility: insulitis in transgenic mice was substantially reduced so that pathology rarely progressed beyond periislet infiltration. This was reflected in a substantial reduction in hyperglycemia and disease. These data indicate that T cells specific for some epitopes of murine Hsp60 are likely to be involved in the islet-cell destruction that occurs in NOD mice.

Expression of mdr1/P-glycoprotein and p110 in neuroblastoma.

Overexpression of the multidrug resistance gene, mdr1, and its product, P-glycoprotein (Pgp), has been associated with cross-resistance to structurally unrelated compounds in cell lines and tumours. Recently, a non-Pgp-mediated form of drug resistance has been described, due to the overexpression of p110, a transport protein. Thirty formalin-fixed, paraffin-embedded neuroblastoma samples from 21 cases were examined for overexpression of mdr1 and Pgp using newly established non-radioactive in situ hybridization and sensitive immunocytochemical techniques. Tumours were examined from patients with all the stages of disease and from primary and metastatic sites. Paired tumour samples (pre-chemotherapy and post-chemotherapy) were available from cases with stage 2 (n = 1) and stage 4 disease (n = 8). Immunoreactivity to p110 was also tested on all the samples. Mdr1 mRNA was expressed in 16/21 cases and in all the stages. Pgp immunoreactivity was detected in all the cases. Weak cytoplasmic immunoreactivity to p110 was seen in the ganglion cells in 12/21 cases. The expression of mdr1, Pgp, and p110 showed a statistically significant (two-sided Fisher exact test, P = 0.04, 0.03, 0.04, respectively) correlation with differentiation (Beckwith and Martin grading) but there was no correlation with survival. Pgp immunoreactivity also showed a significant correlation with favourable clinical variables: age less than 1 year at diagnosis and stages 1, 2, and 4 s (two-sided Fisher exact test, P = 0.01, 0.005, respectively).