Induction of human primary antibody responses in vitro by ovalbumin (OVA) or anthrax (rPA) on dendritic cells (DCs) and follicular dendritic cells (FDCs) in temporally controlled germinal center reactions (GCRs) (47.19)

Abstract

Abstract Induction of potent primary human Ab responses entirely in vitro is challenging, although such in vitro responses could be helpful in assessing vaccines and therapeutics without jeopardizing human health. Given that DCs prime T cells and that FDCs promote B cell responses, we hypothesized that primary Ab responses could be induced in temporally controlled GCRs in vitro. To test this, monocyte derived-DCs were given OVA or rPA for processing, matured with LPS, and CD4+ T cells were added for priming. Ten days later, naïve B cells and OVA or rPA bearing FDCs were added and Ab production was subsequently assayed by ELISA. The CD4+ T cells clustered with DCs through the 10 days of priming and fused with FDC-B cell clusters when GCRs were induced. IgM anti-OVA levels were 79±15 ng/ml 7 days after adding B cells and declined to 2.4±0.5 ng/ml at day 14. In contrast, IgG anti-OVA rose from 9±1.7 at day 7 to 25±6.4 ng/ml at day 14 and the IgG1:IgG2 ratio was 1:3. Similarly, IgM anti-rPA levels were 10 ng/ml by just 5 days then IgM production switched to IgG. IgG anti-rPA rose from 3 ng/ml at day 5 to 9 ng/ml by day 12. In short, Ag specific primary human Ab responses, including Ig class switching from specific IgM to IgG, can be generated in GCRs entirely in vitro. Thus, potential vaccines can be rapidly and safely assessed using the human immune system. (Supported and cleared by DARPA on 12/20/2006 - Approved for Public Release, Distribution Unlimited)