The effects of a thymic peptide preparation (TP) on the immunocytotoxicity and cytokine secretion of peripheral blood lymphocytes and monocytes from patients with colorectal tumors, breast tumors and melanoma were studied in vitro. On average, breast tumor and melanoma patients showed significantly lower natural killer (NK) cell activities than colorectal tumor patients and normal controls. In contrast, the generation of lymphokine (IL-2) activated killer (LAK) cells was found to be comparable within the different tumor diseases (24% cytotoxicity), but lower than in the group of normal controls. TP, being without any effects on NK cell activity in all groups, increased the deficient LAK cell activity of breast tumor and melanoma patients, as well as of normal controls? without significant effects on PBL from colorectal tumor patients. This increase was found to be associated with an increase of the IL-2 induced IFN-gamma and, on a lower level, TNF-alpha secretion, especially from breast tumor and melanoma patients. In addition, monocytes from these patients showed a deranged tumoristatic activity, compared to colorectal tumor patients and normal controls. The stimulation of monocytes by IFN-gamma greatly elevated the mean of the antitumor activity in all groups studied. TP being slightly effective on monocytes from melanoma patients, did not further enhance monocyte-mediated cytotoxicity when applied alone or in combination with IFN-gamma. Reduced basal monocytic chemokine levels were only found in the groups of melanoma (IL-8) and colorectal tumor patients (MCP-1), whereas RANTES secretion was increased, compared to normal controls. TP was active only in reducing the IL-8 secretion of monocytes from colon tumor patients. The results indicate that selected functions of peripheral blood mononuclear cells can be partially improved by the thymic peptide preparation.

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