RELATIONSHIP BETWEEN REDUCTION OF COMPLEMENT ACTIVATION BY POLYSACCHARIDE SURFACES BEARING DIETHYLAMINOETHYL GROUPS AND THEIR DEGREE OF SUBSTITUTION

The relationships between substitution of hydroxyl (OH) by diethylamin oethyl (DEAE) groups on cellulose membranes and the resulting reductio n of complement activation are not clear. As a model, SephadexR has be en randomly substituted with DEAE groups. Modification of 10% of the g lucose units, i.e. about 3% of the groups, had no noticeable effect on the complement activating capacity of the polymer surface, whereas 20 % substitution dramatically reduced it. This result could be explained in part by the fact that Sephadex-specific antibodies are not adsorbe d by this modified surface. Thus, they cannot enhance complement activ ation as they do on Sephadex or cellulose. Comparison of our results w ith those published on HemophanR led us to the conclusion that a simil ar effect could occur. However, the degree of substitution of the memb rane surface is probably greater than that of the membrane core due to the preparation process. Comparison with Sephadex substituted with ot her groups, or with other polymers bearing a variable density of OH gr oups, led us to the conclusion that, as hypothesized by Chenoweth (Art if Organs 1984; 8: 281-287), reduction of the availability of OH group s decreases complement activation, but the relationship is probably no t linear. Moreover, replacement by other groups results in additional modulations due to (i) interactions between the groups and proteins re sponsible for formation or decay of the amplifying C3 convertase and/o r (ii) decrease in recognition of the modified surface by antibodies w hich enhance complement activation on polysaccharides.