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The humoral response of thymus-derived (T) cell-depleted murine spleen cultures was stimulated by the addition of human leukocytes. The stimulatory human cell type was found to be adherent and phagocytic suggesting that it is the monocyte. The stimulation appears to be mediated by a factor released by the adherent cells into the culture medium.
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Wood et al. (1974) studied this question.
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