The cytotoxic T lymphocyte response against a protein antigen does not decrease the antibody response to that antigen although antigen-pulsed B cells can be targets.

The role of activated CD8+ T cells in shaping the dynamics of in vivo antigen presentation and immune responses is a subject receiving more attention. We studied whether cytotoxic T lymphocyte (CTL) would limit antibody responses by targeting antigen-specific B cells. A modified in vivo CTL assay was developed and used herein to demonstrate cytotoxicity in vivo, and to show that antigen-specific B cells that process exogenous antigen and present peptide in association with MHC class I can be the targets of CD8+ T cells. B cells from C57BL/6 mice immunized with ovalbumin (OVA)/alum were pulsed with OVA in vitro, and transferred into C57BL/6 recipient mice that had been immunized with vaccinia virus expressing SIINFEKL minigene to generate CD8+ CTL against K(b)/SIINFEKL. OVA-pulsed B220+ B cells from OVA-immunized mice were killed to a greater extent than B220+ B cells from naïve mice (28+/-20% versus 12+/-16%, p=0.0042). However, mice receiving vaccinia-SIINFEKL and generating CTL, did not appear to target endogenous B cells, since both primary and secondary antibody responses to OVA were unaffected. Our findings indicate that CTL responses to the protein antigen do not interfere with endogenous B cell responses, even though exogenous B cells expressing the CTL epitope can be efficiently lysed.