THE PROGENY OF A SINGLE VIRGIN B-CELL PREDOMINATES THE HUMAN RECALL B-CELL RESPONSE TO THE CAPSULAR POLYSACCHARIDE OF HAEMOPHILUS-INFLUENZAE TYPE-B

Restricted V region diversity is a key feature of Abs so many haptens and simple polysaccharides. Two possible mechanisms exist: 1) selectio n of many clonally unrelated B cells using very similar or identical V DJ and VJ rearrangements; and 2) selection of a heavily expanded proge ny of few virgin B cells, Mow many virgin B cells eventually give rise to the total Ab response to a simple Ag is a fundamental immunologic question, In this report, we address this question in human adults by analyzing the rearranged V kappa J kappa genes of B cells responding t o a single dose of the capsular polysaccharide of Haemophilus influenz ae type b coupled to tetanus toxoid. We combined affinity purification of circulating vaccine-induced Ab-secreting cells with PCR amplificat ion of cDNA followed by cloning and sequencing. Forty-eight and 42 kap pa VJ gene transcripts were analyzed from two adults, respectively, Bo th individuals used extremely restricted repertoires with >90% of the cells using a single V kappa gene rearranged to a single J kappa gene, Despite the fact that the Ab responses engaged high numbers of Ah-sec reting cells,analysis of the many shared, somatically acquired mutatio ns showed that the majority of the cells originated from a common virg in B cell, Kinetic considerations implied that an extremely selected p opulation of hypermutated memory B cells must have existed in these in dividuals before the first systemic immunization with the Ag, A possib le role for the mucosal immune system in the priming and selection of these cells is proposed.