Cross-Priming of Murine B Cells with TNP Conjugates of Hemocyanin and Ficoll: Characteristics of Primed B Cells Responding to Both Antigens

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Abstract
There is strong evidence that separate subsets of B cells respond to primary challenge with TNP-Ficoll (TI.2) and with TNP-KLH (TD). Although TD antigens can prime for responses to TI antigens, it has been suggested that, at least in vitro, distinct subsets respond to TI.2 and TD antigens even after such priming. The present experiments on adoptive secondary immune responses in LAF1 mice suggest that a single population of primed cells may respond to both antigens. This conclusion is based on the findings that 1) High-affinity 7S antibody-producing cells primed by TNP-KLH can be challenged by TNP-Ficoll even after removal of T cells; 2) Priming with TNP-Ficoll induced 2- to 4-fold increased responsiveness to itself and to TNP-KLH, although the maturation with respect to affinity distribution of these IgG responses is significantly less than after priming with TNP-KLH; 3) TNP-KLH primed-cells never give higher responses upon challenge with both antigens simultaneously than to one of these antigens injected alone; 4) Primary and secondary responses to both antigens are reduced to a similar degree after pretreatment of cells with anti-Ia and C; 5) Receptor blockade of TNP-KLH primed cells by incubation with TNP-SIII reduces responses to TNP-KLH by 77 to 90% and to TNP-Ficoll by 60 to 70%. The findings are interpreted as supporting the view that B cell subpopulations responding to TI.2 and TD antigens represent stages of differentiation of a single B cell lineage that are overlapping rather than distinct subsets in vivo.