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A simple method to quantify antigen sites on RBCs was developed. It could be applied whenever one antibody is assumed to bind exactly one antigen.

A new method to find directly complex viscoelastic parameters (CVP) of human red blood cells (RBC) is presented in this paper. Experimental determinations were carried out in an Erythrodeformeter operating in oscillating mode (0.5 to 3.5 Hz). The Erythrodeformeter performs direct determination of CVP of erythrocytes undergoing sinusoidal shear stresses by laser diffractometry. The measurements lead to the determination of mean values of the components of erythrocyte complex viscoelasticity: dynamic elasticity (G'), dynamic loss (G"), viscosity component (r') and elastic component (n") of the complex viscosity (r*). This technique does not use erythrocyte deformability values to calculate complex viscoelastic parameters, we used the phase shift (6) of the erythrocyte response to the oscillating shear stress directly to compute these parameters. The stationary parameters (DI, and im) øbt'ifld using the Erythrodeformeter in stationary regime (Rasia, 1995) provide complementary information on the stationary erythrocyte membrane rheology. The diffractometric method is sensitive to detect different alterations on erythrocyte membrane. Hence, determinations of RBC complex viscoelasticity carried out by laser diffractometry is a very useful tool to investigate erythrocyte rheologic properties and may be relevant to understand some pathological alterations and drug effects on RBC membrane, which can affect the "in vivo" blood flow.

Sir,During the last twenty years there has been an increasing number of publications in which the fact that blood group antigens may act as parasite, bacterium and virus receptors is remarked 3,5,9 .Three concepts have been proposed to explain hosts tolerance for a parasite: mimicry, antigenic modulation and natural selection.The early experimentations which led to the comprehension of the concept of mimicry were performed by CLEGG et al. 2 on Schistosoma mansoni. They demonstrated that larvae in culture may capture A and B antigens and get covered by them.Later investigations based on immunofluorescence and mixed agglutination techniques have demonstrated in vitro adsorption of H, A, B and Le a antigen by Schistosoma mansoni 4,6,8 .In order to perform our experiments Ascaris lumbricoides extracts (AE) were prepared. Adult specimens were washed in physiological solution supplemented with 200 µg/ml of streptomycin and 200 µg/ml of penicillin. After that a refrigerated mechanical rupture was performed for 5 days. The supernatants were collected and kept at -20 °C with a final concentration of timerozal 1:1,000 1,7 .Inhibition agglutination tests were made facing the (AE) against anti A and anti B monoclonal antibodies in optimal concentrations. Suspensions of fresh red cells (A and B groups) were used as a revealing system.Results demonstrated that (AE) of patients having blood group A inhibit agglutination of anti A antibodies with A red blood cells, and (AE) of patients who have blood group B inhibit agglutination of anti B antibodies with B red blood cells.In a second experience these (AE) were faced against sera of patients suffering from ascariasis. (AE) of blood group A patients were found to inhibit agglutination of anti A antibodies with A red blood cells of patients group B (anti A) as well as (AE) of blood group B patients were found to inhibit agglutination of anti B antibodies with B red blood cells of patients group A (anti B).These preliminary experiences suggest that Ascaris lumbricoides may adsorb A and B antigens of the host for antigenic mimicry.Current investigations have a definitive objective: to determine the moment in the life cycle of a parasite in which this adsorption takes place. It might probably be in larval stages in which the parasite moves following the haemetic way.

ABSTRACT--In this work, experimental determinations are carried out using a home-made device called an erythrodeformeter, which has been developed and constructed for rheological measurements on red blood cells subjected to definite fluid shear stress. A numerical method formulated on the basis of the fractal approximation for ordinary and fractionary Brownian motion 1 is proposed to evaluate the viscoelastic behavior of mammalian erythrocyte membranes. The diffraction pattern, which is circular when the mammalian erythrocyte membranes are at rest, becomes elliptical when the cells undergo shear stress. Photometric readings of light intensity variation along the major axis of the elliptical diffraction pattern are recorded during the creep and recovery process. These data series are used to calculate fractal rheological parameters of self-affine Brownian motion on the erythrocytes, averaged over several millions of cells. Three different parameters over the time dependent process could be obtained, which are: correlation coefficient , correlation integral, and K2-entropy, and very different results were obtained.

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SUMMARYA. lumbricoides has been associated to the ABO System by various authors. The objective was to detect ABO System epitopes in A. lumbricoides of groups O, A, B and AB patients. 28 adult parasites were obtained from children to be used as assay material. The patients ABO blood groups were determined. Extracts of A. lumbricoides [AE] KEYWORDS: Ascaris lumbricoides; ABO System; MimicryBlood groups may act as receptors of parasites, bacterias and viruses 2,4,6,8,10 . At present, there is evidence that they perform a function and play a biological role that might not be associated to the erythrocytes 1,7,15 . Ascaris lumbricoides has been associated to the ABO System by various authors 12,13 .The objective of this paper was to detect ABO System epitopes in Ascaris lumbricoides of groups O, A, B and AB patients.28 adult parasites were obtained from children to be used as assay material. The patients ABO blood groups were determined by means of conventional techniques 9 . Extracts of A. lumbricoides [AE] were prepared by surgical remotion of the cuticle and refrigerated mechanical rupture 5,11,13 . Agglutination Inhibition (AI) and Haemoagglutination Kinetics (HK) tests were used with the [AE]. Of the 28 [AE], eight belonged to O group patients, 15 to A group, three to B group and the remaining two to AB children.The AI test showed A epitopes in two pure [AE] of group A patients and epitopes B in two pure [AE] of group B patients. The diluted extracts did not show inhibitory capacity.