Immunochemical studies of lipids. V. Effect of modified hydrophobic moiety on immunogenicity and immunologic reactivity of Forssman glycolipid.

The role of hydrophobic moiety in determining the immunologic properties of glycolipid haptens was studied with the derivatives of Forssman glycolipid modified by ozonolytic cleavage of double bonds in hydrocarbon chains. The immunogenicity was not affected by this modification; comparable antibody responses were elicited in rabbits immunized with intact or modified Forssman glycolipid, regardless of its different hydrophobicity, in complete Freunds adjuvant. Modified hydrophobic portions did not affect the class and specificity of antibodies produced. On the other hand, immunologic reactivity was strongly influenced by hydrophobic moiety; the ability to form immune precipitates with antibodies decreased as the hydrophobicity of glycolipid decreased. The reactivity in complement fixation and hemolysis inhibition tests also showed parallel decreases, though the addition of auxiliary lipids greatly reduced these differences in reactivity. The results indicate the different influences of hydrophobic moiety of glycolipids on their immunogenicity and immunologic reactivity in vitro.