During the past few years, a number of antibody-antigen systems have been examined in considerable detail. Such studies have led to an understanding of many of the basic phenomena associated with the antibody molecule, including structure, antigen interaction, idiotypy and the genetic basis of antibody formation. In most instances, antibodies to small, haptenic determinants such as phosphorylcholine. dinitrophenol, nitrophenyl, arsonate, etc. have been examined. To date, only limited analyses have been performed on antibodies to more complex antigenic determinants such as carbohydrates and proteins. One such system which has been extensively investigated consists of antibodies to^(l, 6) galactan. This carbohydrate is widely distributed in nature and is found in various forms of wheat and in bedding materials to which laboratory mice are continually exposed. Initially, Potter et al.(1972) discovered a series of plasmacytomas whose monoclonal antibodies reacted with this determinant. Subsequently, a series of hybridomas was generated with the same specificity and this combined group has been analyzed to address questions of structure, specificity, idiotypy and genetic mechanisms.