Transient dominance of the early primary immune response by a highly conserved B-cell clone that is distinguished by its lack of memory, high threshold of activation, and a high affinity

We establish here that the very early primary response to the hapten phthalate (Xmp) is distinguished by a restricted heterogeneity with over 80% of the anti-Xmp antibodies expressing a single well-defined cross-reactive idiotype (CRIXmp-1) associated with a previously described highly conserved clonotype that is expressed by most inbred strains of mice and many outbred mouse populations as well. The characteristic early dominance of this one clonotype in the primary response is transient. While the CRIXmp-1 clonotype is present later in the primary and throughout the secondary response, it represents only a very small proportion of the total anti-Xmp antibody population at these times. The early dominance of the single clonotype is rapidly replaced by a heterogeneous population of antibodies. Differential activation thresholds for the primary response clonotype (CRIXmp-1) and secondary response clonotypes, and the failure of the dominant primary response clonotype to expand in the secondary response (i.e., absence of memory) suggest the presence of two distinct B-cell lineages.