B‐Lymphocytes Activated by CD40 Ligand Induce an Antigen‐Specific Anti‐Tumour Immune Response by Direct and Indirect Activation of CD8+ T‐cells

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Abstract
In this report, we describe the ability of CD40‐ligand (CD40L)‐activated, antigen‐loaded B‐cells to initiate antigen‐specific anti‐tumour immune responses in vivo. Mice immunized by means of intravenous administration of CD40L‐activated B‐cells loaded with an MHC class‐I‐binding peptide, and challenged with a tumour cell line expressing the same class‐I epitope, showed a marked delay in tumour growth, compared to non‐immunized controls or to mice receiving either freshly isolated B‐cells or B‐cells activated with lipopolysaccharide or interleukin‐4.The ability of CD40L‐activated B‐cells to induce antigen‐specific T‐cell activation appeared to be through a combination of cross‐presentation of antigen from activated B‐cells to resident antigen‐presenting cells and direct T‐cell activation by the administered B‐cells themselves. Immunization with CD40L‐activated B‐cells may, therefore, represent a means by which to stimulate anti‐tumour CD8+ T‐cell responses in vivo.