Priming of helper T cell‐dependent antibody responses by hemagglutinin‐transgenic B cells

Abstract

Mice expressing the hemagglutinin (HA) gene of influenza virus PR8 (H1 subtype) under the control of kappa light chain promoter and enhancer have been generated. They express HA in and on B cells, and are tolerant to HA. In vitro, only lipopolysaccharide (LPS) blasts but not resting B cells of transgenic mice can stimulate HA-specific helper T cells of HA-specific alpha/beta T cell receptor (TCR)-transgenic mice. Transfer of HA-transgenic LPS blasts into syngeneic, non-transgenic recipients primes HA-specific antibody responses. Resting, small HA-transgenic B cells, which were purified by fluorescence-activated cell sorting, prime lower antibody responses. Host B cells produce the HA-specific antibody response. The donor HA-transgenic B cells need to express major histocompatibility complex (MHC) class II molecules and need to be alive to induce the antibody response in the host. Most notably, the host antibody response never produces detectable levels of IgM, but only of switched IgG isotypes. Neither resting nor activated HA-transgenic B cells induce tolerance in antibody responses. These results suggest that HA-transgenic B cells, presenting both the intact antigen on the cell surface and peptides of the antigen on MHC class II, are effective inducers of helper T cell responses, and as judged by the Ig-isotype response pattern, which is mainly IgG1, of Th2 type.

Successful Interference with Cellular Immune Responses to Immunogenic Proteins Encoded by Recombinant Viral Vectors

“…A previous study, identifying highly immunogenic proteins within the adenoviral backbone, strongly supports this hypothesis (16). This is also supported by experiments using mice expressing HA under the control of the immunoglobulin promoter (18), which drives transgene expression in circulating hemopoietic cells. These mice, which are tolerant for HA, tolerate rAAV-HA but not rAd-HA, indicating that the tissue destruction in the case of rAd-HA is due to an immune response directed against the viral backbone and that rAAV vectors do not break tolerance toward the transgene they encode (data not shown).…”

Regulatory function ofin vivoanergized CD4+T cells

“…To test whether T cell tolerance resulting from ubiquitous expression of HA would prevent muscle fiber destruction after rAd-HA-or rAAV-HA-mediated gene transfer, we tested the immune response to both viral vectors in IG-HA transgenic mice. These mice express the HA antigen under the Ig promoter and enhancer, leading to HA expression on circulating hemopoietic cells (34). As shown in Fig.…”

“…TCR-HA mice, IG-HA mice, and TCR-HA ϫ IG-HA mice, previously described (24,34), are on the BALB͞c background and were bred in our animal facility at Institut Necker. BALB͞c and BALB͞c nude mice were purchased from Iffa͞ Credo.…”

Immune Regulation by Self-Reactive T Cells is Antigen Specific

“…TCR-LACK mice, kindly provided by N. Glaichenhaus, express a TCR␣␤ specific for peptide 156 -173 of the immunodominant Leishmania major Ag, LACK, presented by I-A d (17), and are on a BALB/c background. IG-HA mice, expressing the HA transgene under control of the Ig promoter and enhancer elements (18), were crossed with TCR-HA mice to generate TCR-HA ϫ IG-HA double-transgenic mice. Offspring were typed by PCR.…”