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Two rat monoclonal antibodies (mAbs), 44-22-1 and 46-6B5, which recognize an alloreactive cytotoxic clone, 3F9, have been further tested on a panel of T hybridomas and cytotoxic T-cell clones for binding and functional activities. The mAbs recognized only those cells sharing the expression of the T-cell receptor beta-chain variable region gene V beta 6 with 3F9. All V beta 6+ cells were activated by these mAbs under cross-linking conditions and their antigen-specific activation was blocked by soluble mAb. Furthermore, depletion of 46-6B5+ normal lymph node T cells eliminated all cells expressing the epitope recognized by 44-22-1 and V beta 6 mRNA.

The role of tumor necrosis factor alpha (TNF-alpha) in the pathogenesis of autoimmune diabetes mellitus was tested in the nonobese mouse (NOD) model system. The effects of TNF-alpha were assessed on three levels: (i) insulitis development, (ii) development of overt diabetes, (iii) adoptive transfer of diabetes by splenic lymphocytes. Spontaneous diabetes mellitus was blocked in NOD mice by long-term treatment with recombinant TNF-alpha. Treatment with TNF-alpha caused a significant reduction in the lymphocytic infiltration associated with the destruction of the insulin-producing beta cells. Class II major histocompatibility complex Ia expression by islet cells was not up-regulated by TNF-alpha. Moreover, TNF-alpha was able to suppress the induction of diabetes in adoptive transfer of lymphocytes from diabetic female mice to young nondiabetic male NOD mice. These activities of TNF-alpha were shared by interleukin 1 alpha in this system. These studies have implications for the pathogenesis and therapy of autoimmune diabetes mellitus.

The mechanism of phosphosylation and dephosphorylation of spectrin from human erythrocyte membranes has been examined under closely physiological conditions. The results support the hypothesis that spectrin is an autophosphorylating and dephosphorylating system. (i) Extraction from ghosts of up to 85% of the kinase (casein kinase) suggested to catalyze the reaction [see Fairbanks, G., Avruch, J., Dino, E. J. & Patel, V. P. (1978) J. Supramol. Struct. 9, 97--112] only slightly reduced spectrin component 2 phosphorylation and did not affect ATP-induced changes in the ghosts' shapes. (ii) A spectrin--actin complex isolated from endocytotic inside-out vesicles under hyperteonic conditions contained virtually no casein kinase activity and still exhibited a largely intact phosphorylation machinery. (iii) Photoaffinity labeling experiments indicated that spectrin component 2 fulfills the necessary prerequisite of the hypothesis--i.e., it contains its own ATP-binding site. (iv) Under various conditions, spectrin phosphorylation and dephospohrylation seem to be tightly coupled. The implications of these findings for the understanding of spectrin function and the maintenance of erythrocyte shape are discussed.

The nonobese diabetic mouse is recognized as an important animal model for human insulin-dependent diabetes mellitus. One of the components of susceptibility to this disease has been mapped to the major histocompatibility complex. In this study, full-length cDNA clones encoding the I-A alpha and beta chains from the nonobese diabetic mouse have been isolated and sequenced. They are identical to the sequences previously determined from the H-2d haplotype except for the sequence encoding the first external domain, the leader peptide, and the 5' untranslated region of the I-A beta chain molecule. Most strikingly, there are five consecutive nucleotide substitutions which lead to two radical amino acid changes in a region that is conserved between human and mouse. We suggest that the unique structure of the first external I-A beta chain domain is a major determinant in the disease susceptibility that maps to the major histocompatibility complex of the nonobese diabetic mouse.