LONG TERM IMMUNE MEMORY TO COMPLEX ANTIGENS IN A MOUSE AND A HUMAN MODEL – LONGTERM MEMO B

We propose, in this demand, to study B cell memory following two different experimental approaches that we have recently validated. First, a mouse model in which B cells are irreversibly marked during their passage in germinal centers induced by a controlled immunization, and secondly, a human model in which B cell memory against vaccinia virus is analyzed several decades after vaccination. In the mouse model, the first data we have obtained reveal surprisingly that, in addition to isotype-switched memory B cells, additional B cell subsets with distinct anatomical localization and surface phenotype can be detected more than 8 months after immunization. We want to analyze these different subsets at the molecular (transcriptome), physiological (recirculation properties) and functional (effector/differentiation properties) levels, and to extent this approach to follow T-independent responses that are classically considered as incapable of generating memory. For the second approach, we have recently characterized the human spleen as the storage site for long-lived anti-vaccinia virus memory B cells. They indeed appear to be enriched 3-6 fold within the splenic IgG-positive population, compared to blood IgG+ B cells, with 10-20 million specific B cells residing in the spleen more than 30 years after vaccination against smallpox, and only 50,000-100,000 being present in the blood. By comparing the transcriptome of memory B cells from blood and spleen, we want to identify some markers unique to these cells endowed with long-term memory and survival. We will also enrich for splenic anti-vaccinia virus memory B cells by using their antibody specificity against the dominant vaccinia virus antigenic epitopes. In conclusion, we will ask whether general rules governing B cell memory generated in response to complex antigens can emerge by comparison of these two models