Mitsuyasu Itoh

Abnormal production of B cell growth factor in patients with systemic lupus erythematosus.

In order to clarify the role of B cell growth factor (BCGF) in the pathogenesis of systemic lupus erythematosus(SLE), BCGF production by peripheral blood mononuclear cells(PBMC) and T cells was studied using a new bioassay for BCGF activity. For this purpose, we established an Epstein‐Barr (EB) virus‐transformed B cell line KS‐3.F10 that proliferates only in response to two B cell‐specific BCGF, low‐mol. wt BCGF (LMW‐BCGF) and high‐mol. wt BCGF (HMW‐BCGF). PBMC from active SLE patients produced less BCGF when stimulated with phytohaemagglutinin (PHA) compared with controls. The decreased BCGF production by PHA‐stimulated PBMC from active SLE reverted to control values when SLE became inactive. However, PHA‐stimulated T cells from active SLE patients produced more BCGF compared with controls, whereas those from inactive SLE showed normal BCGF production. Spontaneous BCGF production by T cells was not observed in active SLE patients. These findings suggest that decreased BCGF production by SLE PBMC is due to excessive BCGF consumption by B cells in vitro and that SLE T cells produce large amounts of BCGF with appropriate immune stimuli in vitro to promote polyclonal B cell activation.

Immunological aspects of diabetes mellitus: Prospects for pharmacological modification

It is now well known that insulin-dependent diabetes is a chronic progressive autoimmune disease. The prolonged prediabetic phase of progressive beta-cell dysfunction is associated with immunological abnormalities. A prediabetic period is suggested by the appearance of islet cell antibodies, anti-insulin antibodies, and anti-insulin receptor antibodies. The existence of activated T lymphocytes and abnormal T cell subsets are also other markers. There is still no concensus about the use of the immunosuppression superimposed upon conventional insulin therapy in early diagnosed IDDM and the follow-up of the relatives of IDDM patients who share the genetic predisposition and serological markers for the risk of future onset of IDDM. Treatment in the prodromal period cannot be justified because a link between the disease and early markers such as ICA has not been established with certainty (Diabetes Research Program NIH, 1983). Many immunopharmacological manipulations were reported to be effective in animal models. However, most of them are not readily applied to human subjects. Moreover, IDDM patients are now believed to be heterogeneous, with a complex genetic background. HLA-DR, and more recently DQ, are closely related to the genetic predisposition to IDDM but those genes are not themselves diabetogenic. The contribution of autoimmunity does not appear to be uniform, and in some cases, the contribution of virus is considered more important. There is a lack of a marker for the future onset of IDDM. ICA and ICSA were found after mumps infection, but the existence of those autoantibodies and even the co-existence of HLA-DR3 do not always indicate the future trend to insulin dependency. More precise markers will be disclosed through the biochemical analysis of the target antigens on pancreatic beta-cell for islet antibodies and effector T cells. Much safer and more effective immunopharmacological treatment will be developed through animal experimentation using rat and mouse models. The recent development and interest in this field will further facilitate the attainment of the goal for the complete prevention of IDDM.

Abnormal lymphocyte function precedes hyperglycaemia in mice treated with multiple low doses of streptozotocin.

SummaryTo investigate early immunological disturbances at the onset of diabetes, lymphocyte function and islet cell surface antibodies were studied in streptozotocin-treated C57BL/10 and B10.BR mice. In C57BL/10 mice, streptozotocin given in multiple low doses depressed lymphoblastic transformation to phytohaemagglutinin and pokeweed mitogen, but not to concanavalin A on day 6 after the first administration. On day 20, the transformation remained suppressed with phytohaemagglutinin, but recovered to the control level with pokeweed mitogen. In the early phase after treatment, the islet cell surface antibodies were elevated and then declined. Single high dose administration depressed responses to phytohaemagglutinin with no detectable islet cell surface antibodies. In B10.BR mice transformations to pokeweed mitogen and concanavalin A were suppressed in the early phase. The strain of mice may be a factor to be considered. Thus, it was suggested that the deterioration of immunological function with the formation of islet cell surface antibodies preceded the onset of hyperglycaemia in mice treated with multiple low doses of streptozotocin.

Serotonergic regulation of the spinal cord content of thyrotropin releasing hormone in the cerebellar ataxia mutant mouse.

The effects of serotonin (5-HT) and various serotonin receptor antagonists on the spinal cord thyrotropin releasing hormone (TRH) content were studied in the rolling mouse Nagoya (RMN) and in the unaffected C3H mouse. TRH was extracted from the cervical, thoracic, lumbar, and sacral cord, at 1 h after the intraperitoneal injection of a serotonin precursor, 2 serotonin agonists, and 5 serotonin receptor antagonists. Administration of 5-hydroxytryptophan and 2-methyl-5-hydroxytryptamine resulted in an increase of the spinal cord TRH content in C3H mice, but not in RMN. Parachlorophenylalanine decreased the spinal cord TRH content in C3H mice, while it increased TRH levels in all regions of the RMN spinal cord. The TRH contents were decreased in all regions of the spinal cord after 5,7-dihydroxytryptamine administration in both C3H mice and RMN. In C3H mice, methysergide, mianserin, ketanserin, and spiperone significantly decreased the TRH content in all regions of the spinal cord, while 3 alpha-tropanyl-1H-indole-3-carboxylic acid ester (ICS205-930) did not affect it. These antagonists paradoxically increased TRH levels in the cervical cord in RMN. The degradation of synthetic TRH by cord homogenates and the number and affinity of spinal cord serotonergic receptors (5-HT1 and 5-HT2) showed no significant difference between C3H mice and RMN. These results suggest that TRH turnover is abnormally regulated by serotonergic neurons in the RMN and that the dysfunction of the serotonergic nerves is attributable to the serotonin autoreceptor.

Production of a monoclonal antibody 14A20 that reacts with a 220-kDa protein in the islet cells

To study the target antigens of the islet cell cytoplasmic antibodies (ICA), we tried to make a monoclonal islet cell antibody. We made a monoclonal antibody 14A20 (IgM, kappa) that reacted strongly with Wistar and BB rat islet cells and weakly with pancreatic acinar cells. The immunoreactivity of the 14A20 was also found to react extensively in neuroendocrine cells. Immunostaining showed a granular pattern in both neurons and islet cells. Chemical and enzymic studies revealed that the antigen has the property of a protein. We compared immunoreactivity of the monoclonal antibody 14A20 with anti-insulin, -glucagon or -somatostatin antibodies. The antigen recognized by the monoclonal antibody 14A20 was equally present in the alpha, beta, and delta cells of islet, which mimicked the immunoreactivity of the ICA in the pancreas. The recognized protein had a relative molecular weight of 220,000, indicating that it is different from the previously identified target antigen of the ICA.