Immunologic aspects of insulin

Drug allergy

Although allergic drug reactions are just one type of adverse reaction to medications, they are clinically very important because of the morbidity and mortality they cause. An ever-expanding pharmacopeia increases the potential for allergic drug reactions. An understanding of the types of allergic drug reactions, their immunopathologic mechanisms, and the most likely medications involved; an approach to determine the drug responsible for the reaction; and ways to prevent future allergic drug reactions are important features in minimizing patient morbidity.

Assessment of the antigenic response in humans to a recombinant mutant interferon beta

Cancer patients were given a recombinant mutant interferon beta by alternating IM and IV injections with weekly escalation of doses from 0.1 to 400 million U. Antibodies specific to the interferon of the IgG class were detected in 24 of 30 patients using an indirect enzyme-linked immunosorbent assay. Serum from only 1 of the 30 patients had detectable ability to neutralize interferon biological activity. The in vivo interferon serum level, assayed as antiviral activity immediately after IV injection, was not lower than levels seen in the absence of antibodies. Antibodies did not alter the kinetics of clearance of interferon from the serum after IV administration. Antibody levels progressively decreased when interferon administration was discontinued. In most patients antibody levels decreased during a maintenance period when interferon was being administered only by the IV route. In a subsequent trial interferon was given IV, and antibody developed in only 2 of 36 patients. In contrast, in a trial in which interferon was given IM, 20 of 25 patients developed antibody. No antibody-related clinical sequelae could be detected in any of these patients.

Glucagon secretion in the hibernating edible dormouse (Glis glis)

Plasma glucose and glucagon concentrations were measured in edible dormice during the bout of hibernation, arousal and active periods. During lethargy, plasma glucose and glucagon were low, compared to active values and did not fluctuate throughout the phase. During rewarming, plasma glucose regularly increased from 17 degrees to 37 degrees C while plasma glucagon rose after the 17 degrees C stage and reached the higher values at 26 degrees C, then slightly decreased at 37 degrees C. During arousal, plasma levels of free amino acids progressively increased. The effect of temperature and secretagogue (glucose and arginine) on glucagon secretion was studied using perfused pancreas from hibernating edible dormouse. In vitro rewarming of pancreas induced an increase in glucagon secretion. Glucagon secretion was regulated by glucose (inhibitory effect) and by arginine (stimulating effect) up to 25 degrees C. The effect of temperature and glucagon on oxygen uptake of hibernating edible dormouse brown fat was studied using an in vitro technique. Rewarming strongly increased oxygen consumption from 10 to 37 degrees C. Glucagon enhanced oxygen consumption up to 20 degrees C.

Virus persists in beta cells of islets of Langerhans and is associated with chemical manifestations of diabetes

Molecular hybridization, monoclonal antibody, and electron microscopic analyses showed lymphocytic choriomeningitis virus (strains Armstrong and WE) persistently infecting cells of the islets of Langerhans in BALB/WEHI mice. When monoclonal or monospecific antibody conjugated with two different fluorochrome dyes was used to mark insulin-containing beta cells or viral antigens, viral nucleoprotein was identified predominantly in beta cells. Electron microscopy confirmed these findings by showing virions budding from the beta cells. Persistent infection was associated with chemical evidence of diabetes (hyperglycemia, abnormal glucose tolerance, and normal or low-normal concentrations of insulin). Concentrations of cortisol and insulin-like growth factor in blood were normal, as was the level of growth hormone in the pituitary gland. The virus-infected islet cells showed normal anatomy and cytomorphology. Neither cell lysis nor inflammatory infiltrates were routinely seen. Thus a virus may persistently infect islet cells and provide a biochemical and morphological picture comparable to that of early adult-onset diabetes mellitus in humans.

Pancreatic A cell response to arginine in the hibernating hedgehog (Erinaceus europaeus)

Pancreatic A cell response to arginine was measured in hedgehogs during the periods of lethargy and arousal and then during activity. Spontaneous plasma glucagon concentrations were lower during lethargy than during activity, and they increased during arousal. Arginine administration induced a slight, but significant delayed increase in plasma glucagon concentration in the lethargic hedgehog (body temperature: 6 degrees). During arousal, in vitro glucagon secretion was temperature dependent suggesting that body rewarming might, in itself, be an important stimulating factor of the A cells. In the presence of arginine, the glucagon output of the pancreas of lethargic hedgehogs was high at low temperatures. It decreased to a nadir at 19 degrees and increased up to 37 degrees. However, the basal or arginine-stimulated glucagon secretion of animals in lethargy was higher than that of animals in activity. These characteristics suggested the presence of a particular pool of cold-adapted enzymes in the A cells of lethargic hedgehogs.

Factors that control insulin action at the receptor

The binding of insulin to its plasma membrane receptors is an important component of insulin action at the cellular level. Insulin binding is altered in a number of clinical disease states in humans, and several specific regulators of the receptor have been identified. Recent in vitro studies of receptor regulators have furthered our understanding of the interaction of insulin with its receptors and also increased our awareness of the complexity of this interaction. The importance of the plasma membrane environment around the receptor, the potential importance of receptor microaggregation to information transfer, and the coupling of receptor binding to insulin action are reviewed.

Insulin allergy and insulin resistance: two immunologic reactions

Insulin allergy and insulin resistance can cause life-threatening problems for diabetic patients. Fortunately, allergic manifestations are usually localized, but increasingly severe local reactions can precede a systemic reaction. How use of newer and purer insulin preparations than those previously available will affect the incidence of immunologic reactions is yet to be determined.

The syndromes of insulin resistance and acanthosis nigricans. Insulin-receptor disorders in man

In six patients with acanthosis nigricans variable degrees of glucose intolerance, hyperinsulinemia and marked resistance to exogenous insulin were found. Studies of insulin receptors on circulating monocytes suggest that the insulin resistance in these patients was due to a marked decrease in insulin binding to its membrane receptors. When these patients were fasted, there was a fall in plasma insulin but no increase in insulin binding, suggesting that the receptor defect was not secondary to the hyperinsulinemia. The clinical features shared by these cases and several similar ones previously reported may be divided into two unique clinical syndromes: Type A, a syndrome in younger females with signs of virilization or accelerated growth, in whom the receptor defect may be primary, and Type B, a syndrome in older females with signs of an immunologic disease, in whom circulating antibodies to the insulin receptor are found.

Pathogenesis, diagnosis and treatment of diabetic ketoacidosis

The diagnosis of diabetic ketoacidosis must be suspected and the initiation of treatment should be prompt to provide a satisfactory outcome in the treatment of diabetic ketoacidosis. Corrections of fluid and electrolyte deficiencies should be made slowly; rapid "push"injections or large infusions of sodium bicarbonate should avoided and ample amounts of potassium should be given early. Precautions should be taken so that blood glucose concentrations do not fall rapidly, and so that blood glucose levels of 250-300 mg/100 ml are maintained by the administration of 5-10% glucose solutions. Bicarbonate therapy is indicated only in severe acidosis (pH less than or equal to 7.1). Physicians who are trained in the care of diabetes mellitus should supervise the treatment. In our hospital the same staff physicians and fellows attend all patients with diabetes. In addition the efforts of our house staff and nurses have contributed significantly to the care of these patients.

Treatment of severe diabetes mellitus by insulin infusion

A new and simple form of insulin therapy for diabetic hyperglycaemia and ketoacidosis has been developed using a continuous intravenous infusion of insulin at a rate of 2.4 U/hr to maintain serum insulin concentration at physiological levels. This rate raises the mean serum insulin to 83 muU/ml and has a therapeutic effect which is not augmented by higher infusion rates. The response to such low doses of insulin indicates a need for a reappraisal of currently held theories about insulin resistance in diabetic ketoacidosis. In 11 diabetic patients with a mean plasma glucose of 514 mg/100 ml this therapy produced continuous falls in plasma glucose at a mean rate of 75 mg/100 ml/hr, and 10 out of 11 patients recovered within eight hours. This form of therapy is simple to institute, not complicated by hypoglycaemia, and avoids the confusion and empiricism of previously described forms of therapy.

Effects of various drugs on insulin antibodies

1. Insulin antibodies were induced in young guinea-pigs of both sexes weighing 300-400 g and housed in a room maintained at 28 degrees C+/-2 degrees C, by subcutaneous injection of 2 ml of freshly prepared insulin antigen emulsion between the shoulders once every month.2. To estimate the titre of serum antibody the serum was incubated with a known concentration of insulin for 90 min at 37 degrees C and the insulin not bound to antibody was estimated by the rat hemidiaphragm method.3. No significant (P>0.5) development of insulin antibody could be detected in the serum samples collected 1 month after the first and 15 days after the second monthly injections in groups of ten male guinea-pigs and six female guinea-pigs. However, the titre of insulin antibody in the serum of these groups of guinea-pigs 15 days after the third monthly injection of insulin antigen emulsion was significantly (P<0.01) raised. There was no further increase in the titre of insulin antibody in the sera 15 days after the fourth and fifth monthly injections of insulin antigen emulsion. Thus the peak titre was reached 15 days after the third monthly injection of the antigen.4. Two groups of ten male guinea-pigs each received testosterone propionate or diethylstilboestrol daily for 1 week after each monthly injection of insulin antigen emulsion. Two other groups of six female guinea-pigs each received testosterone propionate or diethylstilboestrol in a similar manner. One more group of ten female guinea-pigs received both sex hormones for 1 week after each monthly injection of insulin antigen emulsion. Testosterone facilitated the induction of insulin antibody in the serum of males but did not affect the antibody titre in the female guinea-pigs. Diethylstilboestrol facilitated the induction of insulin antibody in the serum of groups of either sex, the peak titre being attained after the second monthly injection of insulin antigen emulsion. The response of the females which received both sex hormones was similar to that of females which received diethylstilboestrol alone.5. Fifteen days after the third monthly injection of insulin antigen emulsion a group of ten guinea-pigs received hydrocortisone subcutaneously each day for 1 month. The serum antibody titre was estimated at the end of the drug treatment, and was significantly (P<0.01) reduced.6. Fifteen days after the third monthly injection of insulin antigen emulsion three different groups of five-six guinea-pigs each received tolbutamide, chlorpropamide or phenformin orally every day for a month. Antibody titres of the serum were estimated at the end of this period; there was no significant (P>0.05) reduction in groups receiving chlorpropamide or phenformin, but the serum antibody titre of the group receiving tolbutamide was significantly (P<0.01) raised.7. Fifteen days after the third monthly injection of insulin antigen emulsion different groups of five-six guinea-pigs received one of the following: 5-bromouracil, 5-fluorouracil, 6-mercaptopurine, methotrexate, 6-azauridine, busulphan, chlorambucil, cyclophosphamide, actinomycin-D or mytomycin-C intraperitoneally each day for 5 days. The serum antibody titre of all the groups of guinea-pigs was significantly (P<0.01) reduced. On the other hand the serum antibody titre of a control group of six guinea-pigs receiving normal saline intraperitoneally each day for 5 days was not significantly (P>0.5) affected.

Human serum proinsulin

Gel filtration of human serum extracts on Bio-Gel P-30 columns produced two peaks of material reactive with insulin antisera. The earlier eluting fraction appeared at the elution position of proinsulin (serum proinsulin-like component, PLC) while the second fraction corresponded in elution volume to insulin. In assays using porcine insulin-(131)I and an antiserum against porcine insulin, human pancreatic proinsulin was less reactive than human insulin. Serial dilutions of the serum PLC in the immunoassay showed immunological identity with the human proinsulin standard. Partial tryptic digestion of the serum PLC yielded products with increased immunological reactivity as estimated with insulin as the standard. With larger amounts of trypsin, all the serum PLC was converted to insulin-like components (desthreonine and desoctapeptide insulin). On the basis of these results we conclude that the earlier eluting fraction of human serum extracts is proinsulin. The fasting values of proinsulin in normal subjects ranged between 0.05 and 0.4 ng/ml, representing from 5 to 48% of the insulin concentration. In one subject the values of proinsulin were higher than those of insulin. After oral administration of 100 g of glucose, the proinsulin levels tended to rise similarly to insulin. Three obese patients with hyperinsulinemia had higher fasting levels of proinsulin and a greater increase after glucose than the normal subjects. As the high levels of proinsulin coexisted with raised insulin concentration in these obese subjects, the relative proportions of the two hormones were in the same range observed in the normal group. Thus hyperinsulinemia in these obese subjects was not accompanied by an increase in the fraction of serum proinsulin. When the values for serum proinsulin were expressed as percentage of the insulin levels, there was a decrease in the per cent proinsulin in the first hour of the glucose tolerance test. After the second hour, the per cent tended to rise towards the fasting levels.

Serum-insulin response to glucose in "pancreatic diabetes"

Thirty patients with chronic pancreatitis (mostly calcific) were tested for glucose tolerance and serum insulin response to glucose loading. The responses were very variable and the insulin values did not clearly relate to the ‘glucose-tolerance-status’. Some subjects had low insulin levels throughout, some had average to high fasting levels without further response, and some showed an excellent rise of insulin level after glucose.

No antibodies to insulin could be found in seven patients. Synalbumin antagonist was present at 1·25% in five out of twelve patients tested.

ACTH antibodies in patients receiving depot porcine ACTH to hasten recovery from pituitary-adrenal suppression

Six patients who had experienced prolonged steroid-induced pituitary-adrenal suppression were treated with 100 U of depot procine ACTH every 2 to 4 days for several months. Such treatment did not hasten the recovery of normal pituitary-adrenal function compared with the rate of recovery of a group of similarly suppressed patients who received no depot ACTH. Eight of nine patients who received prolonged courses of depot porcine ACTH developed antibodies to ACTH that cross-reacted with endogenous ACTH, binding it in the circulation in inactive form and retarding its removal from the circulation. The presence of such antibodies did not in itself grossly alter pituitary-adrenal interrelationships.

Application of newer concepts in diabetes

The changing definition of diabetes, brought up to date, includes the concepts of premellitus as well as mellitus, and of an enzymatically impaired or otherwise ineffective insulin as the possible cause of the full syndrome. Another current concept holds that an increased amount of this lipogenically active but glycolytically impaired insulin is the mechanism producing obesity in diabetes as a premellitic sign. Despite changed concepts the importance and effectiveness of prophylactic weight control in the premellitic stage, and as the fundamental treatment in all stages of obesity-diabetes remains the same. The order of preference in the addition of specific drugs to the dietary treatment of obesity-diabetes is anorexigenic agents, phenformin, single sulfonylureas, and combined chlorpropamide-phenformin. Insulin is the therapy of last resort in this usually mild form of diabetes. There is great potential usefulness for oral hypoglycemic combination therapy (with steroids temporarily if necessary) as a replacement for insulin in the treatment of immunologically-produced insulin resistance.

Immunological response to the prolonged administration of heterologous and homologous insulin in cattle

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Antigens in Insulin Determinants of Specificity of Porcine Insulin in Man

Porcine insulin, which is distinguished from human insulin only in the amino acid at the C terminal of the B chain, is antigenic in man. Even if the last amino acid or the last eight amino acids are removed from the C terminus of the B chain of insulin, the altered insulin still reacts with human antibodies to porcine insulin; thus, the antigenic determinant of porcine insulin is located in a part of the molecule where the amino acid sequence is the same as it is in the corresponding part of the human insulin molecule.