Immune reactions of platelets and their clinical significance

Acute thrombocytopenic purpura and poststreptococcal acute glomerulonephritis in a child

The occurrence of acute idiopathic thrombocytopenia purpura in association with poststreptococcal glomerulonephritis in a 5 1/2-year-old boy is described. This association has been reported only in two cases in the literature. We are reporting the first biopsy-proven confirmation of this association.

Significance of circulatory immune complexes in thromboangiitis obliterans (Buerger's disease)

Circulatory immune complexes were estimated in the sera of 25 patients and 20 age and sex matched controls by precipitation with 8% polyethylene glycol (PEG). Characterization of the immune complexes, thus obtained, was performed by the double immuno-diffusion method. The mean protein content of the PEG precipitates was significantly higher in the patients of thromboangiitis obliterans than in the controls. The immunoglobulins in the immune complexes were predominantly of mixed type in contrast to mainly single class immunoglobulins in the controls. C3 complement distribution in immune complexes of patients and control sera was 64% and 45% respectively. The immune complexes in patients were found to be biologically active. The mechanism of formation of circulatory immune complexes and their role in the pathogenesis of arteritis in relation to smoking of tobacco has been postulated.

Detection of quinidine-specific antibodies with platelet 125I-labeled staphylococcal protein A test

Remarkably higher titers (80--160) of quinidine-specific antibodies were detected in the serum of 5 patients with suspected quinidine purpura, when 125I-labeled staphylococcal protein A was used as the marker of IgG bound onto platelets. During a follow-up of 3 of the patients, the antibody titers declined. The antibodies could be detected even when the final drug concentration was reduced from 0.3 to 0.003 mmol/l (i.e. therapeutic levels). The reaction between serum and platelets was independent of the type of quinidine salt used. No cross-reactivity occurred with quinine. Heat inactivation of the serum did not decrease the quantity of specific antibodies detected on the platelets. The sedimentation behavior of antiplatelet activity in density gradient centrifugation resembled that of 7 S antibodies. When sedimentation was, however, effected on the drug-serum mixture, the reactivity of 7 S decreased.

Studies on the platelet radioactive anti-immunoglobulin test

A platelet radioactive antiimmunoglobulin test (PRAT) has recently been introduced. In the present report, a detailed analysis the influence of varying test conditions (i.e. efficiency of iodination of anti-IgG, cell number, degree of sensitization of platelets, times and temperatures of incubation, frequency of washings) on the results of this technique is presented. A standard procedure based on these findings is outlined. It is shown that the PRAT is two to four times more sensitive than platelet complement fixation for the detection of HLA antibodies.