Dendritic cells (DC) are the professional antigen presenting cells of the immune system. Therefore, several clinical studies have been initiated in which tumor antigen-loaded DC are used as a vaccine to boost an immune response against malignant tumors in patients with cancer. A prerequisite for DC used in these vaccination studies is not only that they are grown under "Good Manufacturing Practice" but equally important that they retain their functional properties. In an extensive study, various conditions were tested to optimize the maturation and yield of DC grown for clinical use. DC grown in XVIVO-15 medium supplemented with 5% HS yielded the best results, morphologically and phenotypically. Mature DC expressed significant amounts of mature DC markers (CD83) and the costimulatory molecules CD80 and CD86. It was shown that mature and immature DC can be frozen and retain their phenotype and function after thawing. These clinical grade DC secreted high levels of the chemokines dendritic cell chemokine1 (DC-CK1), interleukin-8 (IL-8), macrophage-derived chemokine (MDC), and thymus and activation-regulated chemokine (TARC). This implicates that these DC can attract naive T and B cells as well as natural killer cells and memory T cells. Finally, to test their migratory capacity in vivo, (111)In-labeled DC were injected into tumor-free lymph nodes of patients with melanoma. Autoradiographic analysis of the dissected lymph nodes indicated that these DC could migrate into the T cell area of adjacent lymph nodes. In conclusion, a culture procedure was established to generate large numbers of monocyte-derived immature and mature DC that retain their morphologic, phenotypic, and functional characteristics in vitro and can be visualized in situ.
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