The role played by leucocytes and platelets in anaphylactic and peptone shock

Immune reactions of platelets and their clinical significance

It is recognized that blood platelets with a peculiar cell membrane which carries numerous genetically determined immunogens, but is also intricately associated with the hemostatic process not only participate in immune reactions as a passive target cell, but also as an active functional cell. Pertinent results of animal experiments and of in vivo and in vitro investigations with human blood platelets are reviewed in the attempt to elucidate the role of immune reactions of platelets in the pathogenesis of various human bleeding disorders.

Concentration of histamine in different parts of the brain and hypophysis of rabbit: effect of treatment with histidine, certain other amino acids and histamine

1. Estimates have been obtained by biological assay of the histamine concentration in different parts of the rabbit brain and hypophysis.2. Mean values (ng/g) for the brain were: hypothalamus, 660; central grey matter and medial thalamus, 275; tegmental region of mid-brain, the hind-brain and caudate nucleus, 140 to 170; hippocampus and cerebral cortex, 90 to 110; cerebellum (vermis), 60.3. The mean value (ng/g) for the anterior lobe of the hypophysis was 650; for the posterior lobe, 400.4. In conscious rabbits, intravenous infusion of histidine in the dose range 62 to 1,500 mg/kg, raised significantly (P<0.01) the concentration of histamine in all regions of the brain examined, the pattern of distribution remaining unchanged. The largest increases occurred in the mid brain (90 to 320%) and in the hypothalamus (50 to 250%); in these areas the higher doses produced higher concentrations. Elsewhere in the brain the concentration rose in response to the lowest dose of histidine, but was not increased when higher doses were given. Concentrations in the anterior lobe of the hypophysis were unaltered.5. The infusion of histidine, unlike that of amino acid precursors, of the monoamines, produced no obvious disturbance in the animals.6. The rise in brain histamine after dosage with histidine persisted for several hours, depending on the dose; with 500 mg/kg, the rise was virtually unchanged after 16 hours.7. Histamine (5 mg/kg by intravenous infusion) raised the concentration of histamine in the hypophysis but not in the brain.8. After the infusion of DOPA, alpha-methyldopa or 5-hydroxytryptophan, the histamine concentration rose in the mid-brain but not in other parts of the brain.9. These amino acids, when infused singly with histidine, did not interfere with the histidine-induced rise of brain histamine.

Acute systemic anaphylaxis in the horse

1. Histamine in small doses caused systemic depressor responses in horses, whereas greater doses caused biphasic effects. All doses of 5-hydroxytrypt-amine (5-HT) were pressor and all doses of bradykinin depressor. All three active substances raised pulmonary artery pressure and lowered central venous pressure. 5-HT reduced ventilation volume. Histamine caused brief apnoea followed by hyperpnoea only.2. Acute anaphylaxis in the horse was accompanied by a severe systemic arterial depressor response, a pressor response in the pulmonary artery and vena cava, and alternating phases of apnoea and dyspnoea.3. During anaphylaxis, profound haemoconcentration, leucopoenia, thrombocytopoenia and hyperkalaemia were in evidence. Early during anaphylactic shock (2 to 4 min) there were profound increases in plasma histamine (five to six-fold) and plasma kinin activity (four to five-fold). Plasma 5-HT concentrations were reduced initially but recovered. Later in anaphylaxis (10 to 20 min) whole blood histamine concentration fell significantly. This coincided with the most profound period of leucopoenia.4. No significant differences were observed in histamine concentration in any of five tissues between six ponies subjected to anaphylaxis and six controls. Mast cell numbers were not reduced but mast cells were more metachromatic (pink) and there was spilling of mast cell granules.5. Gross pathological changes were noted mainly in the lungs which were extensively oedematous and congested. Inflamed, congested and oedematous areas in the large colon and caecum were seen, and the kidneys, spleen and liver were engorged. Alveolar emphysema, peribroncheolar oedema (containing mononuclear cells and neutrophils) were recorded. Alveoli contained erythrocytes.

A THROMBOCYTE CONSUMPTION TEST FOR THE DEMONSTRATION OF AUTOANTIBODY-LIKE SERUM FACTORS

The capacity of blood platelets to attach themselves aspecifically to antigen-antibody complexes in the presence of complement can be utilized for the demonstration of antibodies formed against homologous tissues.A mixture of the serum-, antigen-complement, and of human thrombocytes is incubated, and the number of thrombocytes in the supernatant is ascertained and referred to a standard. Measurements less than 85% of the standard are regarded as positive. Sera collected from patients with ;protracted' acute or chronic hepatitis and cirrhosis were found to be positive with the new method in 68.0% of the cases; the corresponding figures were 26.3% for ;non-protracted' acute hepatitis and 18.1% for diseases of the bile duct. No positive reaction occurred in other internal diseases studied or in healthy persons, but 40% of subjects with diverse infections gave positive results possibly because of autoantibody formation against tissues damaged by the infections. Comparative examinations suggest that the thrombocyte consumption test is more specific than the antihuman globulin consumption method.

Immediate Effects of Intravenous Endotoxin on Serotonin Concentrations and Blood Platelets

Adult mongrel dogs were given a lethal dose of E. Coli endotoxin by rapid intravenous injection. Total serotonin levels in the serum fell rapidly, with the concentration in the portal vein and pulmonary artery significantly exceeding that in the femoral artery within the first minute after injection. Small rises in plasma serotonin were found in some of the animals. These changes were coincident with a sharp fall in the number of circulating platelets, with striking changes in platelet morphology, and with the initial fall in blood pressure.