Role of Dendritic Cells in the Immune Response Induced by Mouse Mammary Tumor Virus Superantigen
AUTOR(ES)
Baribaud, Frédéric
FONTE
American Society for Microbiology
RESUMO
After mouse mammary tumor virus (MMTV) infection, B lymphocytes present a superantigen (Sag) and receive help from the unlimited number of CD4+ T cells expressing Sag-specific T-cell receptor Vβ elements. The infected B cells divide and differentiate, similarly to what occurs in classical B-cell responses. The amplification of Sag-reactive T cells can be considered a primary immune response. Since B cells are usually not efficient in the activation of naive T cells, we addressed the question of whether professional antigen-presenting cells such as dendritic cells (DCs) are responsible for T-cell priming. We show here, using MMTV(SIM), a viral isolate which requires major histocompatibility complex class II I-E expression to induce a strong Sag response in vivo, that transgenic mice expressing I-E exclusively on DCs (I-EαDC tg) reveal a strong Sag response. This Sag response was dependent on the presence of B cells, as indicated by the absence of stimulation in I-EαDC tg mice lacking B cells (I-EαDC tg μMT−/−), even if these B cells lack I-E expression. Furthermore, the involvement of either residual transgene expression by B cells or transfer of I-E from DCs to B cells was excluded by the use of mixed bone marrow chimeras. Our results indicate that after priming by DCs in the context of I-E, the MMTV(SIM) Sag can be recognized on the surface of B cells in the context of I-A. The most likely physiological relevance of the lowering of the antigen threshold required for T-cell/B-cell collaboration after DC priming is to allow B cells with a low affinity for antigen to receive T-cell help in a primary immune response.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=112858Documentos Relacionados
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