Complement-independent precipitin lines in double diffusion analysis of anti-hapten sera and hapten protein conjugates may show spurs within a single haptenic system. This phenomenon is observed when anti-DNP antibodies are analyzed with DNP conjugates with different numbers of haptenic groups. A spur is observed when the line formed by the highly conjugated antigen joins the line of the lesser conjugated antigen. This phenomenon is explained by the formation of soluble antigen-antibody complexes between antibody and DNP-BSA of relatively low degree of conjugation which are precipitated by DNP-BSA of high degree of conjugation. A similar finding is observed with the cross-reacting haptenic system—pentaCIB-DNP. An anti-pentaCIB serum causes the formation of a precipitin line with highly conjugated DNP-BSA which spurs over that formed with pentaCIB-BSA conjugated to a lesser degree. In anti-hapten systems spur formation of complement independent precipitin lines is not entirely predictable upon the basis of antigenic relationship.

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Supported by Public Health Service Grant AI04983 and the Health Research Council of the City of New York, Contract I-138.

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