Kazuyuki Ohbo

Molecular cloning and characterization of a novel glycoprotein gp34, that is specifically induced by the human T-cell leukemia virus type I transactivator p40tax

We have cloned and sequenced a cDNA encoding gp34, a novel glycoprotein expressed in cells bearing human T-cell leukemia virus type I (HTLV-I). HTLV-I has a trans-acting transcriptional activator, p40tax, that is thought to be implicated in leukemogenesis through the activation of cellular enhancers. With a subline (JPX-9) of the human T-cell line Jurkat, in which p40tax is inducible, gp34 was shown to be of cellular origin and to be transcriptionally activated by p40tax. It was also demonstrated that two species of mRNA are generated from one copy of the gp34 gene and that these mRNAs encode the identical gp34 product and differ in the 3 untranslated region. Analysis of the deduced amino acid sequence of gp34 showed that it lacks typical signal peptides; however, it has a hydrophobic stretch for membrane anchoring and four possible N-linked glycosylation sites at the carboxy-terminal portion, indicating that it belongs to the family of membrane proteins whose carboxy-terminal portion protrudes out of the cell. The gp34 gene displayed relatively delayed induction compared with other genes activated by p40tax. Taken together with the observation of the dependence of gp34 expression on HTLV-I p40tax, unlike other p40tax-dependent genes such as those for the interleukin-2 receptor alpha chain and c-fos, which are expressed or induced under physiological conditions, we predict that the mechanism involved in the induction of gp34 expression by p40tax is distinct from and more intricate than those for the previously characterized genes.

Cerebrospinal fluid interleukin 6 in amyotrophic lateral sclerosis: immunological parameter and comparison with inflammatory and non-inflammatory central nervous system diseases

We assayed IL-6 in 105 cerebrospinal fluid (CSF) samples from patients with ALS, MS, HTLV-1 associated myelopathy (HAM), and controls. There was considerable overlap in IL-6 levels in all patient groups. The mean IL-6 in 27 patients with ALS was significantly higher than in 21 patients in the other neurological disease (OND) group (P=0.0075). There were no significant differences in MS or HAM and the OND control group. Overall, CSF IL-6 correlated with protein concentration but not with percentage IgG or IgG-albumin index. Patients with CSF oligoclonal bands were no more likely to have detectable IL-6 than patients without oligoclonal bands. Similarly, IL-6 did not correlate with clinical disease activity in MS when subgroups of patients were compared or when an individual patient was followed over time. The elevated IL-6 in ALS may reflect an ongoing humoral immune response, or IL-6 may be non-specifically expressed in these patients as a putative neurotrophic factor in response to nerve cell degeneration.

Interleukin‐6 in cerebrospinal fluid of HTLV‐I‐associated myelopathy

We demonstrated significant titers of interleukin-6 (IL-6) in the CSF from 6 of 11 patients with HTLV-I-associated myelopathy (HAM). The patients positive for IL-6 generally had more severe clinical symptoms and signs than those negative for IL-6. There was no correlation between the value of IL-6 and inflammatory findings in the HAM CSF.

Lymphohaematopoietic abnormalities and systemic lymphoproliferative disorder in interleukin-2 receptor γ chain-deficient mice

Interleukin‐2 (IL‐2) receptor γ chain‐deficient mice with a truncated mutation showed the absence or severe reduction of natural killer cells, decreased numbers of T‐ and B‐u2003cells, marked hypoplasia of the thymus and peripheral lymphoid tissues, defective formation of lymphoid follicles and germinal centre in the peripheral lymphoid tissues, and the absence of Peyers patches in the intestinal mucosa. In addition, marked splenomegaly with extramedullary haematopoiesis, increased level of IgM and decreased levels of IgG and IgE in serum, severe reduction of conventional B cells (B‐2) in the peripheral lymphoid tissues, the presence of IgM‐producing CD5+ B cells (B‐1) and their differentiation into plasma cells and Motto cells in the spleen, and increased production and differentiation of macrophages in various tissues were found in the mutant mice. However, the development of both marginal metallophilic macrophage populations in the spleen and of their related macrophages in the other tissues of the mutant mice was severely impaired. All these abnormalities seem to be induced by the loss‐of‐function of the IL‐2 receptor γ chain. From 8 weeks of age on, inflammatory changes occurred in the intestines, mesenteric lymph nodes, lungs, liver, and kidneys of the mutant mice. Besides the absence of Hassall’s corpuscles, thymic cysts were frequently observed in the mutant mice. These pathological abnormalities suggest that the γ chain is implicated not only in lymphoid and haematopoietic development but also in thymic epithelial cell ontogeny.

Monoclonal antibodies defining distinct epitopes of the human IL-2 receptor β chain and their differential effects on IL-2 responses

We have established and characterized five new monoclonal antibodies (mAbs) which specifically immunoprecipitate the human interleukin-2 receptor beta chain (IL-2R beta). One of them, TU30, recognizes the intracytoplasmic serine-rich region of IL-2R beta that is critical for IL-2 signal transduction. The others, TU12, TU21, TU23 and TU25, completely inhibit IL-2 binding, as does the previously characterized TU27. However, reciprocal binding competition assays show that the epitopes recognized by the individual mAbs are different from each other. The mAbs inhibit the growth of IL-2-dependent cells. The magnitude of their inhibitory effects is dependent on not only the affinities of the mAbs for IL-2R beta but also upon the number of IL-2R alpha subunits expressed on IL-2-dependent cells. These mAbs should be useful in studying the structure and function of the IL-2R.