SUMMARYThere are physiological variations in the levels of leucocytes. Among these, the circadian rhythm is very important in terms of the magnitude. Since newly identified lymphocyte subsets (i.e. extrathymic T cells) have recently been detected, a comprehensive study of the circadian rhythm was conducted. All leucocytes were found to vary in number or proportion with a circadian rhythm and were classified into two groups. One group-granulocytes, macrophages, natural killer (NK) cells, extrathymic T cells, gd T cells, and CD8 þ subset-showed an increase in the daytime (i.e. daytime rhythm). The other group-T cells, B cells, ab T cells, and CD4 þ subset-showed an increase at night. Humans are active and show sympathetic nerve dominance in the daytime. Interestingly, granulocytes and lymphocyte subsets with the daytime rhythm were found to carry a high density of adrenergic receptors. On the other hand, lymphocyte subsets with the night rhythm carried a high proportion of cholinergic receptors. Reflecting this situation, exercise prominently increased the number of cells with the daytime rhythm. These results suggest that the levels of leucocytes may be under the regulation of the autonomic nervous system.

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Serum I-FABP measurement is a non-invasive method that is potentially useful for the efficient identification of patients with acute abdomen who are at risk of small bowel ischemia.

SUMMARYSelf-reactive clones, estimated by anti-Vb monoclonal antibodies (mAb) in conjunction with the Mls system, are confined to a population of intermediate (int) T-cell receptor ( TCR) (or CD3) cells (i.e. TCRint cells), but are not found among TCRhigh cells. The next questions to be answered are whether autologous killing is confined to TCRint cells and how such killing is mediated. In this study, 51Cr-labelled thymocytes of syngeneic or allogeneic origin were used as target cells (4-hr assay). When liver and splenic mononuclear cells (MNC ) obtained from B6 mice were used as eÂector cells, prominent autologous killing was seen in liver MNC, but not splenic MNC. Such killing was not seen when thymocytes from B6-lpr/lpr mice (i.e. Fas−) were used as target cells, nor when liver MNC from MRL-gld/gld mice (i.e. Fas ligand−) were used as eÂector cells (target thymocytes of MRL-+/+ mice). Cell separation experiments using a cell sorter revealed that autologous killing was mediated for the most part by CD3int cells, while allogeneic killing was mediated entirely by natural killer (NK ) cells, TCRint cells and TCRhigh cells. Among CD3int cells, the NK1.1+ subset (i.e. NK1.1+ T cells) manifested a higher level of autologous killing than did the NK1.1− subset. Consistent with the results of a functional assay, it was found by reverse-transcription-polymerase chain reaction ( RT-PCR) assay that CD3int cells among liver MNC showed the expression of Fas ligand mRNA, while thymocytes expressed Fas mRNA. When class I major histocompatibility complex (MHC )− thymocytes (from b 2 -microglobulindeficient mice) were used as target cells, NK cells, but not CD3int cells, showed potent cytotoxicity. These results suggest that autologous killing is a major function of TCRint cells with self-reactivity, and that such killing is mediated by means of Fas ligand/Fas molecules.

It is believed that self‐reactive forbidden T‐cell clones are generated by ‘failure’ of the pathway of T‐cell differentiation in the thymus, if it is disturbed. We examined how such forbidden clones are generated under immunosuppressive conditions. Mice were treated with an injection of deoxyspergualin, FK506, or cycloporin A. From day 3, the number of cells yielded by various organs decreased. Because of the resistance of intermediate (int) T‐cell receptor (TCR) cells (i.e. TCRint cells), they became more prominent in proportion than TCRhigh cells. TCRhigh cells are conventional T cells generated through the mainstream in the thymus, whereas TCRint cells are primordial T cells generated by the extrathymic pathway or an alternative intrathymic pathway. Similar to untreated mice, forbidden Vβ3+ and Vβ11+ clones in C3H/He (Mls‐1b2a) mice were confined to TCRint cells after treatment; there was no leakage of forbidden clones into TCRhigh cells in the thymus and periphery. In parallel with the increase in the proportion of TCRint cells, the proportion of forbidden clones also increased under immunosuppressive states, especially in the liver. Liver mononuclear cells isolated from treated mice still had the potential to mediate autologous killing. The present results suggest that the generation of self‐reactive clones is highly restricted to the pathways of TCRint cell differentiation even under immunosuppressive conditions.

The thymus comprises the mainstream of T cell differentiation which produces conventional T cells and an alternative pathway which produces primordial T cells with intermediate density of T cell receptor (TCR)-CD3 complex on the surface (i.e. intermediate TCR cells or TCRint cells). We induced acute thymic atrophy in mice by an administration of hydrocortisone (10 mg) or irradiation (6.5 Gy). It was demonstrated that CD3intCD4lowNK1.1+ T cells were immediately generated by an alternative intrathymic pathway without passing through the double-positive CD4+8+ stage, when restored from thymic atrophy (days 3-14). These CD3intCD4lowNK1.1+ T cells mediated self-reactivity and appeared even in the periphery. mRNA of an invariant chain of TCR Valpha14Jalpha281 gene product was detected in these CD4low T cells, but not remaining CD4high T cells. The mainstream of T cell differentiation in the thymus was not restored up to day 14 and there was no leakage of self-reactive clones into the population generated through the mainstream. These results reveal that an alternative intrathymic pathway is associated with the generation of self-reactive T cells, in an early restoration phase after thymic atrophy.

This study confirmed a positive survival effect with NIV, which was less effective in patients with bulbar dysfunction. Additional studies are required to determine the best timing for using NIV with ALS in patients with bulbar dysfunction.

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