Inducement of antitumor-immunity by DC activated by Hsp70-H22 tumor antigen peptide

Objective: To investigate the feasibility of decreasing the dosage of tumor antigen peptides by dendritic cell (DC)-presenting and the characteristics of modification of DC by heat shock protein (Hsp70) and antigen peptides. Methods: Peptides were bound to Hsp70 and used to modify DC in vitro . The metabolism of the modified DC and the cytokines secreted by the modified DC were determined. The activation of lymphocytes by the modified DC and Hsp70-H22 peptides was tested. The cytotoxicity of the activated lymphocytes to H22 tumor cells was analyzed. The inhibitory effect of tumor in mice by the injection of DC and Hsp70-H22 peptides was tested. Results: 0.15 µ g of H22 peptides bound with Hsp70 could make 2 ×10 5 DC mature. 4×10 3 matured DC could activate 2×10 6 lymphocytes. The same amount of lymphocytes could be activated to produce similar cytotoxicity to tumor cells by either DC modified by 0.003µg of peptides bound with Hsp70 or by direct stimulation with 0.15 µg of peptides bound with Hsp70. The dosage of peptides could be reduced by about 50 folds if the modified DC was used for injection instead of Hsp70-peptides. Peptides from normal hepatocytes, bound with Hsp70, could not make DC mature, nor activate lymphocytes through DC. Conclusion: The dosage of Hsp70-H22 peptides can be reduced significantly by DC-presenting to activate lymphocytes. Peptides from normal cells could not activate lymphocytes by either Hsp70-presenting or DC-presenting and they have little chance to induce autoimmunity.